Chapter 4: Breaking the Ice in a Locked Room
Mitsumura led us to the east building, to the room next to where Mr. Manei had been killed. That was the same room Mitsumura and I had experimented with the dominoes earlier that day. It seemed Mitsumura was planning to finish that, performing an experiment to recreate the locked room in which Mr. Manei was killed.
“Well, here we go.”
Mitsumura opened the inward swinging door and ushered us into the room. There were dominoes lined up there. Actually, I was the one who'd lined them up, and I hadn't cleaned them up when I left, so it would be more accurate to say “dominoes had been left in the room”. Apparently she was planning on recycling them.
Everyone was in the room except for Yashiro, who was still fatigued from his brush with death. Everyone's eyes followed the path of the dominoes on the floor.
In the center of the room was a stuffed bear Mitsumura had brought over. It was the same one from the House of Snow Locked Room Case. Apparently, he was being asked to play the victim again.
And around the bear, dominoes were lined up in the shape of a sideways U. It looked like the square had been cut in half vertically. The left half of the square had a side with a length of of 2 meters. The right side didn't exist.
Mitsumura began.
“The important aspects of this locked room are the dominoes on the right side of this square, which aren't currently present, and the ones extending from the bottom of the square towards the door, which also are not currently present. How we arrange those dominoes... will be the key to creating the locked room.”
Everyone nodded in agreement. Of course, that was the hard part.
“So, how on Earth are you going to do it?” asked Dr. Ishikawa. “Using this,” Mitsumura said, picking up the thing she'd prepared earlier and showing us.
It was crafted out of cardboard. There were two pieces: a U-shaped piece of cardboard about as wide as a ski, and another, straight piece about 2 meters long, also the width of a ski. The pieces all had thicknesses of about 1 cm, so it might have been more accurate to call them “very skinny cardboard boxes” rather than pieces. Dominoes had been stuck at regular intervals on both the U-shaped and straight pieces. This was the mysterious object Mitsumura had been working on in the lobby earlier. Mitsumura laid out the cardboard. First, she placed the U-shaped piece to the right of the bear/corpse. Everyone exclaimed in realization. The U-shaped piece matched with the dominoes to the left of the bear, forming a square with two meter sides. The U-shaped piece had identical measurements to the missing right half of the square.
Mitsumura then placed the remaining straight piece so that it touched the bottom edge of the square. The straight piece now extended towards the door. “What do you think?” she asked.
“It's a wonderful recreation of the scene where Mr. Manei was killed, isn't it?”
Indeed, the dominoes went in a straight line from the door before colliding with another set of dominoes forming a square – it was exactly the same as the situation inside the locked room of Mr. Manei's room. That was, if you ignored the pieces of cardboard the dominoes were stuck to.
“What's the point of this?” Riria asked. “It's true that it looks like the scene at the time, but the culprit still can't leave the room.”
Mitsumura looked completely unperturbed. “I'm not finished yet,” she said, and went back to work. She grabbed the straight, two meter long piece and stuck one end to the door with cellophane tape. The door and the piece were now attached. She used more cellophane tape to attach the straight piece to the U-shaped piece. The door, straight piece, and U-shaped piece were now all connected.
After finishing her work, Mitsumura looked around the group. Her eyes stopped on Yozuki.
“Yozuki.”
“Y-Yes?”
“May I have a little help?”
“...You want me to play assistant again?”
Having been nominated, Yozuki reluctantly stepped forward. Apparently, she'd rather have been in the audience, listening to her reasoning. However, when Mitsumura said “This is a job only you can do,” she immediately said “I understand” and pumped a fist. Yozuki was easily manipulated like that.
“So what do I do?” the assistant asked the detective. The detective replied as follows:
“Open the door and go out into the hallway. Then, close the door. That's it.”
“...Is that really a job only I can do?”
The assistant had her doubts. But in the end, Mitsumura was able to admonish her into going out in the hall. Yozuki grabbed the doorknob, turned it, and pulled. And at that moment, everyone gasped.
“What is it?” Yozuki looked down at her feet in surprise. They'd moved. The dominoes stuck to the cardboard pieces were all fixed to the door with cellophane tape, so they swung with the door as it opened and closed.
Was this it? Was this the trick?
“Now, Yozuki, please go out into the hallway and close the door.”
Yozuki timidly stepped out into the hallway. Then she slowly closed the door. And as she did...
The cardboard affixed to the door also moved. There were two pieces, the U-shaped one and the straight one. When viewed from the hallway side, the door's hinge was on the right. Therefore, the door rotated to the right when it opened, and to the left when it closed. So, when she opened the door earlier, the two pieces fixed to the door had swung to the right, and the dominoes on the cardboard had temporarily swung away from the ones on the left half of the square. But when Yozuki closed the door, they cardboard swung back to the left as though rewinding the image – and reattached itself to the left of the square, reforming the ring around the bear. From the bottom edge of the square, the dominoes still extended towards the door. They were in the exact same state as they were before the culprit, Yozuki, left the room.
“This is the secret of the locked room of the dominoes.”
Everyone gasped in admiration at Mitsumura's words. But they soon realized that nothing had actually been resolved. “What about the pieces of cardboard?” asked Fenrir. “How do you collect them from the crime scene?”
Mitsumura shrugged.
“You don't,” she said with a small smile. “I used cardboard here for convenience, but the real culprit used ice.”
I was confused for just a moment, but I quickly realized what she meant.
“You mean the ice melted and the pieces the dominoes were stuck to disappeared?”
“Yes, and if they raised the temperature in the room with the heating, it would melt faster. Also, the flooring in Mr. Manei's room was rougher than in the other rooms. Therefore, the water from the melted ice would have sank into the floor much more easily than in another room, although it didn't dry completely. The floor was a little damp.”
I did remember that the floor at the crime scene was damp. I'd thought it was just ordinary dampness, but maybe it could have been a sign that this trick was used.
But I still had my doubts.
“But that means this trick could have only been used in the room with the rough floor, right?” I asked. “But it must have been a coincidence that Mr. Manei stayed in this room. If Mr. Manei had stayed in a different room, how could the culprit had pulled off this trick?”
After all, the other rooms had waxed, polished floors. If that much ice had melted in one of them, the water would have remained on the floor. In that case, the fact that this was a trick using ice would have been revealed in a second.
Mitsumura shook her head and said “Perhaps you have it backwards?”
“Backwards?”
“Yes, backwards,” she nodded. “Perhaps the culprit originally intended to spill a drink on the floor to cover up the water from the ice? Such that the water from the ice would mix with the drink and no longer be perceptible? But they noticed that the floor of this room was rough, so they thought there was no longer the need. The traces of the trick would disappear overnight without them needing to spill the drink anyway, so the culprit modified their original plan to suit the situation.”
I found that convincing. It would have been possible to use this trick in any room, but by coincidence, Mr. Manei wound up staying in a room perfectly suited to it.
I understood that much. Then the only remaining mystery is...
“How did they prepare the ice slabs for the trick?” I asked. A two meter long, straight board made of ice, and another one of the same size in the shape of a U. They were too big to make in a freezer.
But Mitsumura had an answer.
“They used liquid nitrogen,” she said, turning to face Miss Meirozaka. “I heard in the lobby that Miss Meirozaka found a suspicious looking water bottle in the building's storeroom earlier?”
Miss Meirozaka nodded.
“Yeah, what's up with that?”
“That bottle wasn't full of water, but liquid nitrogen. The culprit filled that bottle with liquid nitrogen and brought it to the hotel. After the crime, they disposed of it in the storeroom.
I did remember the water bottle. Certainly, it seemed more airtight than a regular water bottle. But I'd never considered the possibility that it contained liquid nitrogen. Why was Mitsumura so sure of this?
As if she sensed my doubts, Mitsumura said “I've seen it on the internet before.”
“Internet?”
“Yes, the internet. I searched 'liquid nitrogen container' on Amazon, and a bottle exactly like that came up. I remember being impressed that Amazon even sells things like this.”
Having explained all the issues, Mitsumura stroked her black hair and finished explaining the trick.
“The specific way you make an ice slab is to first prepare a thin, rectangular, two meter box with no top, made out of cardboard or something similar. Line up the dominoes at regular intervals inside. Pour in the liquid nitrogen, and it will rapidly freeze into a straight slab. The U-shaped piece was the same, just use a U-shaped box instead of a straight one.”
“Liquid nitrogen was also used to affix the straight piece to the door and the other end to the U-shaped piece. For example, to affix the straight board to the door, they wet the door with water, touched the end of the slab to it, and poured liquid nitrogen over it. The slab would be affixed to the door.”
“However, if they were concerned whether it would be strong enough, they may have also prepared an entire separate slab. For example, an L-shaped piece with a hole the size of a fist at the end of the horizontal bar, which they turned to hook the hole onto the doorknob. They then firmly attached the piece on the doorknob to the door with liquid nitrogen. Then, they connected the straight piece with the dominoes to the bottom of L-shaped piece hanging from the door. In that way, the ice would be affixed all around the doorknob, increasing its strength, and the amount of connection between the ice piece and the door would increase, also increasing its strength.”
When she was finished, she looked at everyone with cool, measured eyes.
“That is the solution to the Incomplete Locked Room used to kill Mr. Manei. However, there is another mystery in this murder. I will now explain the Complete Locked Room.”
The scene where Mr. Manei's body was found was something-that-may-or-may-not-have-qualified-as a double locked room. Not only was the door blocked by the dominoes, but it had also been locked. And Mitsumura said that she was about to unlock it.
“I haven't told you all yet, but there was one very important thing about this locked room. That is that the deadbolt on the door had been cut by the perpetrator. Therefore, this might not actually qualify as a Complete Locked Room as defined by the Ministry of Justice. A Complete Locked Room refers to a locked room with no noteworthy features. Strictly speaking, a locked room with a cut bolt should probably be a Semi-Complete Locked Room.”
“We don't need all these complicated explanations!” Riria interrupted Mitsumura's explanation. “What did the culprit do?”
“They used a simple trick.”
“It was that easy?” Riria asked. Mitsumura shook her head.
“'Simple” and 'easy' are different words. This is an extremely clever trick. I've taken to calling it 'the autolocking door.”
Autolocking door?
“Oh, so the door locked itself automatically?” Yozuki blurted out. “Like the autolocks at hotels?”
“Yes, it was like that,” Mitsumura said with a nod. “But I'm sure I don't have to remind you that Mr. Manei's room didn't have that sort of autolock. Despite that, it did automatically lock.”
...She could have been a bit more straightforward.
“Well, evidence speaks louder than words.”
Mitsumura went out into the hall and went to Mr. Manei's room next door. Apparently, her “autolocking door” trick could only be recreated in Mr. Manei's room, the actual scene. The reason for that was...
“This is the severed deadbolt.” Mitsumura pointed to the bolt protruding about five millimeters from the open door. “This bolt is the key to the autolocking door trick. Although its been cut shorter, this has no effect on its functionality as a lock.”
Mitsumura tried to close the door with the deadbolt sticking out. However, the 5 mm of bolt still protruding hit the door frame and stopped it. She pushed as hard as she could, but it wouldn't close.
“There you have it. So, what do we do?” Mitsumura casually pulled out the cellophane tape from her pocket. “We use this.”
Her plan declared, Mitsumura turned the thumb turn about 20 degrees. Usually, locking or unlocking a door requires you to turn the thumb turn 90 degrees, but she only turned it 20. But that 20 degrees was enough to retracted the deadbolt protruding from the edge back into the door. What? “Ah, I get it,” said Miss Meirozaka.
“Since the bolt was cut short, you only have to turn it a little to get it back inside the door.”
Mitsumura nodded at her.
“Yes, originally, the deadbolt wouldn't retract unless the lock was turned the full 90 degrees, but since the bolt has been shortened, it is now completely hidden by rotating it only 20 degrees. And now, we secure this 20 degree rotated thumb turn in place with tape, like so.”
As Mitsumura said, she gently fixed the turn halfway in place with tape. “All we do now is close the door like this.” Mitsumura closed the door. With the bolt retracted, it closed without resistance. Mitsumura declared,
“The autolocking door trick is now ready.”
All our faces turned into question marks. She'd prepared a trick? When?
“What part of this is the autolocking door trick?” I blurted out. Mitsumura shrugged at me and said “Just wait a minute.”
We flashed question marks again.
In the end, we decided to wait quietly, as Mitsumura asked. She'd prepared a trick... We stared at the thumb turn, which was still secured with tape. At first, nothing changed, but after about a minute, a strange, faint noise reached our ears. It was coming from the cellophane tape holding the thumb turn in place.
That sound was...
“The cellophane tape peeling off?”
The moment I said those words, the tape ripped off completely, and the lock, which had been turned about 20 degrees, returned to a horizontal position. At the same time, we heard the sound of the deadbolt slamming into place. We all went “Eh?” in perfect harmony.
“There you have it.” Mitsumura pulled the doorknob. We heard the bolt catch. The door wouldn't open. It had been locked.
Automatically.
“This is the Autolocking Door Trick.”
Mitsumura declared her victory.
“W-What's happening here?” Yozuki asked in confusion as she looked at the autolocked door. “Why did the lock lock itself?”
Admittedly, I was as confused as Yozuki. Even though there had been no force applied to the lock, it had twisted itself back into position. No matter how much I thought, I couldn't see the logic behind it.
Mitsumura, however, did have an answer.
“It's simple logic. They just took advantage of the inherent properties of the lock.”
It was an inherent property of the lock?
“Generally speaking, this kind of thumb turn deadbolt lock has a spring inside,” Mitsumura said. “Since there's a spring, if you only twist the thumb turn a little, the spring will force it back to its original position. Like this...”
She grabbed the thumb turn and twisted it the 20 degrees again. She let go. Then, with the sound of a spring, it returned to its original position. Mitsumura shrugged a bit.
“You see? The thumb turn always points either straight vertically or straight horizontally, doesn't it? It never gets stuck halfway. Haven't you ever wondered why? It's because the lock itself has the ability to correct its orientation... for whatever reason. So, as I've demonstrated, the lock will automatically return to its original position if you only twist it part way. However, if its internal spring is deteriorated, or was weak from the beginning, it might not reset properly, but luckily for the culprit, this room's lock is...”
“The type with a powerful spring?” I asked.
I remembered when I was investigating this room with Mitsumura, she turned the lock from the inside and I heard the sound of a powerful spring.
Mitsumura nodded at me.
“However, it would be impossible to use this trick if you didn't know that thumb turn locks have this property. However, everyone here, even Kuzushiro, has used thumb turn locks thousands of times, so whether you realize it or not, you've had countless opportunities to realize it in the course of your lives. And that applies to the culprit, too. Today, they chose to use this property to create a locked room.”
This was the Autolocking Door Trick created by the culprit. All they had to do was put the cut off piece of the deadbolt into the receiver in the door frame with a bit of adhesive on the end, and when the door was locked, the two pieces would collide and become stuck together again.
So then the remaining problem was... I looked at the cellophane tape used to hold the lock in place. It was still stuck to the thumb turn.
“How did they retrieve the tape?”
“Oh, that.” Mitsumura answered me immediately. “I used cellophane tape for the demonstration, but in reality, the culprit used liquid nitrogen. With the thumb turn twisted, pour some water on it and freeze it with liquid nitrogen to secure it in place. That way, the ice would melt over time and the lock would be free, right? That way, there would be no traces left at the scene, so they wouldn't have to retrieve anything from inside the room.”
Having finished her speech, she ran her fingers through her black hair.
“That is all the tricks used in the fourth locked room, where Mr. Manei was killed. Now, let us go to the dining hall. I will explain the Broad Locked Room where Ms. Shihai was killed.”
Following Mitsumura's instructions, we went to the dining hall. She gathered us near the south side wall where Ms. Shihai's body had been and began talking about the crime, saying “Let's begin by reviewing the situation of the locked room.”
“From 5:00 A.M. to 8:00 A.M. on the day of the crime, the door leading to the dining hall was monitored by Kuzushiro and others from the lobby. Ms. Shihai's estimated time of death was between 6:00 and 7:00 A.M. At 8:00 A.M., everyone in the hotel at the time was gathered together in the lobby. That means that no one was able to kill Ms. Shihai in the dining hall. So, what does that mean? I believe this can be resolved with a remote murder.”
“Remote murder?” I asked, tilting my head. “On the subject of remote murder,” Fenrir said, also tilting her head.
“I had the impression they were primarily used in alibi tricks. Are you saying this one was used in a locked room murder?”
“Yes, Miss Fenrir, you must know that remote murders can be used in locked room tricks as well as alibi tricks. You understand, right, Kuzushiro?”
I nodded at her.
Indeed, remote murders could be used in locked room tricks. For example...
“Say the culprit put Ms. Shihai to sleep with drugs or something,” I said. “Then they moved her to the couch where she was found and set up a remote murder trick in the dining hall. Then, they left the dining hall, all before 5:00 A.M. If the remote murder trick went off between 6:00 and 7:00 A.M., the estimated time of death, the dining hall would have been a locked room at that time, so they culprit would have committed a locked room murder. Even though they were outside at the time of the murder... they'd have been able to kill Ms. Shihai inside the locked room.”
In other words, it was possible to kill Ms. Shihai without going into the room at the time it was guarded, allowing them to create the locked room we found. That was... if we ignored the staggering contradiction in that theory.
But I couldn't do that.
“Ms. Shihai was stabbed five times in the chest.”
“Indeed, I was about to bring that up myself,” said Fenrir. “There are several tricks to remotely stab a person, but the most common is to connect some sort of timer to a device that launches the blade, so that at the proper time, the blade is sent flying, killing the victim. In this case, the weapon is a halberd, so when the time came, the halberd would have gone flying into Ms. Shihai's chest. Certainly, there are no problems up to that point. The problem is that Ms. Shihai was stabbed five times. In other words, after the halberd was stuck in her once, it was pulled out, then stabbed in again. They repeated that action five times in total.”
Fenrir's blue eyes looked straight into Mitsumura's.
“So I wonder. Is it really possible to use a remote murder trick to stab someone five times in the chest?”
A heavy silence fell over the room.
It was impossible. Everyone could see that. Of course, it may have been possible if a large, complex mechanical device, but since the scene was a locked room, that device would have remained at the scene. The culprit couldn't have entered the dining hall until the locked room was resolved – at which point the remote murder device would have been found at the scene.
That's why Mitsumura's reasoning was wrong... we thought. However, the girl in question didn't seem to think so, and after giving us a placid smile, she said:
“It is possible. You can stab a victim in the chest with the halberd as many times as you please, and leave almost no trace at the scene.”
Everyone's eyes went wide. She raised her index finger and added “Probably.”
“As you'd expect, this trick can't be performed without some tools. We will use a certain tool. Now, what tool will we use? I'll give you a hint: It's something that's still here in the dining hall.”
We were suddenly hit with a pop quiz. Even if she asked about tools... “Maybe... it's a table?” Yozuki said. “That tablecloth looks suspicious.” There didn't appear to be any logic behind her answers.
In the end, we all gave up quickly and went back to looking to Mitsumura for answers. After shrugging her shoulders, she plainly stated the answer to her quiz.
“What tool did the culprit use?” Mitsumura pointed at it with her index finger. “The cupboard.”
We were all stunned.
What she pointed at was the cupboard built into the wall next to where the corpse had been. The body sat about two meters away from it, and it had a faint splattering of blood. It was just an ordinary cupboard. ...Wait. No it wasn't.
“That cupboard is...”
Mitsumura nodded at me. “Yes, it's this,” she said, pulling a remote control from her pocket. She pointed it at the cupboard and hit the button.
Suddenly, the cupboard slid to the right.
The empty space was exposed. There were a set of stairs down to the basement. That's right, the cupboard was...
“The entrance to the hidden room.”
The only hidden room in the House of Snow.
“But so what if there's a hidden room?” asked Miss Meirozaka. “I don't see how it can be used for a remote murder.”
Mitsumura nodded in agreement.
“Yes, the hidden room itself has nothing to do with the trick. What the culprit used was the cupboard itself.”
“The cupboard?”
“Yes, because...”
Mitsumura pressed the button again. The cupboard slid violently to the side, covering the hidden room. Then she pressed it again. The cupboard slid quickly over.
“This cupboard moves pretty quickly, doesn't it?”
Mitsumura threaded her fingers through her hair and said:
“So I thought, if they fixed the halberd to the cupboard, they might be able to stab the victim multiple times.”
“So you're saying they used the sliding movement of the cupboard to stab Ms. Shihai to death?”
Mitsumura nodded at me. Then she said “To be precise...” She approached a table and pulled out a stick that had been hidden under the tablecloth. It looked like a handle that had been removed from a broom, and a paper knife had been attached to one end of the handle. Apparently, it was playing the role of the halberd's spear tip that was the murder weapon. The spear was also perpendicular to the handle, so it was almost the same shape.
“I'll affix this to the cupboard.”
Mitsumura said that and placed one end of the stick on the shelf of the cupboard. The cupboard was empty, so there was plenty of space. She used duct tape to secure it in place. The tip of the knife on the handle stuck out like a clock hand. If there had been someone sitting on the couch, it would have been aiming directly at their chest.
“And if we open the hidden room like this...”
Mitsumura pressed the button.
The cupboard jerked sideways. That made the tip of the “knife” attached to the handle dart towards the chest of the imaginary person on the couch.
“They'd have been stabbed,” Mitsumura said. And then she pressed the button again. This time, the cupboard slid back the other way, and the knife once again went with it. “Now the knife has been removed.”
We were all stunned. This would make it possible to stab the victim multiple times. The cupboard was located to the right of the corpse sitting on the couch, and the cupboard had a width of about two meters. When the hidden room was opened, it moved about a meter. In other words, if you fixed the halberd's handle to the shelf and placed the tip of the spear about a meter away from the victim's chest, the blade would pierce them when the hidden room was opened, and be removed when it was closed.
The distance between the location where the corpse was found and the cupboard was about two meters, and the halberd's length was also about two meters – in other words, the corpse was the optimal distance from the halberd's spear to perform the trick. Furthermore, the corpse was sitting deep in a single seat couch, so even if they were repeatedly stabbed hard in the chest, they wouldn't have lost their balance or fallen off.
“Generally speaking, remote controls work by...” Mitsumura held up the remote in question, “...Using infrared rays, so they can operate if they're used through a window. The culprit probably activated this remote murder trick from outside that window using the remote.”
Where Mitsumura pointed was the window on the west wall of the dining hall, in the southwest corner. So, the culprit had been outside the window between 6:00 and 7:00 A.M., the estimated time of death, when they activated the trick through the window.
“But if that were the case, wouldn't the halberd be stuck to the cupboard?” Dr. Ishikawa pointed out. “But it was lying on the floor when we found Ms. Shihai's body.”
Indeed, it was as he said. The halberd had been found on the floor. Although its handle was pointing towards the cupboard, it wasn't attached to it.
So, how did the culprit remove the halberd from the cupboard? Mitsumura immediately presented an answer.
“Simple. They affixed it with liquid nitrogen.”
“Liquid nitrogen again?” I asked.
“Yes, this is its third appearance today.”
Was the culprit was getting kickbacks from the liquid nitrogen industry? Sure, it was convenient, but this was getting ridiculous. “They used it, and I'll explain how,” Mitsumura continued.
“There was a decorative cloth about the size of a hand towel attached to the end of the halberd's handle, correct? The culprit soaked that cloth in water, tied it to the handle, and froze it with liquid nitrogen. That made the cloth usable as an adhesive to fix the halberd in place. The halberd is just a plastic imitation, so it is quite light. However, if the ice were too thin, the halberd would have come off the shelf before the trick was activated, so they had to be careful with how much water they used.”
As I listened to her explanation, I remembered something. Come to think of it, the halberd's cloth had been soaked when we found the body. That was a remnant of the trick that had been left at the scene.
“Then, the culprit added the final touch.” Mitsumura held up the remote again. “They turned on the heating through the window. This remote control opens the hidden room, but it is also the remote control for the heating. And do you all recall? At the time the body was discovered, this dining hall... was as hot as a midsummer day. Ms. Shihai was killed between 6:00 and 7:00 A.M. that day, and her body was discovered at 8:00... That means that from the time of the murder to the discovery, there were at absolute most two hours. The culprit had to completely melt the ice used to affix the halberd to the cupboard in those two hours.”
“So the culprit used the heater to melt the ice?”
“Yes, they did,” Mitsumura said. “And ironically, that decision is what made me realize who the culprit is.”
“Raising the temperature lead to the identity of the culprit?”
Everyone, myself included, wore dumbfounded expressions. Only Mitsumura kept her usual cool face.
“When they raised the temperature, the room became as hot as in midsummer. So, in order to lower it back down, Miss Yozuki picked up the remote control that had been left on a table by the window. And that led me to the identity of the culprit. That remote must have been outside the dining hall between 6:00 and 7:00 A.M., when Ms. Shihai was killed. Otherwise, the cupboard couldn't have been moved, the remote murder trick couldn't have been used. And the dining hall was locked until 8:00 A.M., so the culprit couldn't have returned it to the dining hall before then. The remote control was already on the table when Miss Yozuki went to use it to lower the temperature – after we returned from Mr. Sagurioka's room.”
“So in other words, the culprit had to have returned the remote control to the dining hall between the time Ms. Shihai's body was discovered and the time we returned to the dining hall.”
“Yes, that's exactly right,” Mitsumura said with a nod. “And there is only one person who could have done that. So, the person who had a chance to return the remote to the dining hall is the culprit.”
Was there someone who had that opportunity?
“But I'm pretty sure anyone could have returned the remote to the dining hall.” When Miss Meirozaka said that, Mitsumura shook her head.
“No, that isn't true. The remote was placed on the table by the north window of the dining hall. If someone had left the body to approach the window, we would have noticed. So, nobody could have returned the remote until after we all left the corpse – in other words, when we all left the dining hall to go to Mr. Sagurioka's room.”
Come to think of it, Mitsumura had asked about that earlier. She had wanted to know if it was possible to approach the window without being noticed. Was this was she was worried about?
Then...
“The same applies to when we got back to the dining hall,” I said. “If someone had gone near the window then, we would have seen them. The first person to approach the window was Yozuki, and the remote was already on the table by that point. So by the time we got back to the dining hall, it had already been returned?”
“Yes, that's how it was,” Mitsumura said, stroking her black hair. “In summary, the culprit returned the remote between ① When we all left the dining hall and ② when we all returned to the dining hall.”
In other words, between ① and ②, the culprit returned to the dining hall without anyone seeing.
...Wait a minute. But at that time...
“We were all together.”
Because we all went to Sagurioka's room as a group, and we all returned as a group. If someone had tried to sneak off back to the dining hall, their absence definitely would have been noticed.
Mitsumura answered my concern with a simple “Yes, we were.”
“But there was one moment when they could have returned the remote. It's simple. If everyone left the dining hall to go to Mr. Sagurioka's room, then the dining hall was empty... The culprit was the last person to leave the dining hall.”
The last person to leave?
“And Kuzushiro remembered who left the dining hall and when,” Mitsumura said. “According to him, Miss Meirozaka was the first to leave, followed by Dr. Ishikawa, Miss Fenrir, and Mr. Manei. Miss Yozuki and I went after. Kuzushiro was the second to last person to leave the dining hall. In other words, the person who left after him is the culprit.”
I searched my memories of that time. I was, indeed, the second to last person to leave the dining building for the central building. As I was walking down the hall, I heard a mournful voice behind me. I turned around and saw someone there.
“Which means you are the culprit.”
Mitsumura spoke in a cool, even tone.
“Miss Riria, you are the Locked Room User.”
Riria broke into a grin, but she quickly fixed it into an artificially flustered expression.
“Wha? What are you even talking about?” Riria said to Mitsumura. “How could you suspect widdle ol' me of murder? You're such an idiot.”
“But, Miss Riria, you are the only one who could have returned the remote to the dining hall,” Mitsumura retorted. “That means you're the only one who could have performed the remote murder trick using the cupboard. Remember? When Ms. Shihai's body was discovered, the dining hall was as hot as in midsummer, but the heater itself had been set to a normal temperature. That means the temperature had only been set back to normal very recently. The only person who would have needed to raise or lower the temperature at the crime scene is the criminal, right? And the dining hall was a locked room from 5:00 to 8:00; no one could have gone in or out. In other words, if the temperature hadn't been lowered through the window, it would have had to have been lowered before 5:00, when the dining hall became a locked room. That wouldn't explain why it was still at midsummer temperatures by 8:00. It should have decreased at least a little. In other words, it's proven that the remote was outside the dining hall between 5:00 and 8:00 – the culprit either turned the temperature down through the window, or turned it down while they were returning the remote after the dining hall. Either way, the only one who could have done so was the only one with a chance to return the remote to the dining hall – that is to say, Miss Riria. If you are not the murderer, why did you take the remote control from the dining hall?”
Riria paused in thought for a moment and said “That's...” But eventually, she gave up and shook her head slightly. She looked somewhat happy.
“Nah, let's not. I was beaten as soon as you saw through all the locked rooms, anyway. Making up excuses at this stage would go against my glamour girl image.”
Her impossibly innocent voice stopped for a moment. Then it came back to say:
“That's right, I'm the Locked Room User.”
Her confession froze us all in place. I asked in disbelief.
“Are you really the culprit?”
“That's right, this ultra-kawaii girl is actually a stone cold killer! Kyaa! So cute. But aaaghghghgh...” she scratched her head in frustration. “I made a real big oopsie, didn't I? I went to all the trouble of waking up Mr. Manei early to guard the lobby door and create a Broad Locked Room, but now it's all been a total waste. The remote was on that table originally, so I thought it would be less suspicious if I left it right back where I found it.”
Riria's bold declaration seemed to stuff my head with cotton. When I finally found my voice, all I could say was a generic line.
“Why did you do all this?”
She answered me with a cruel smile.
“It's all business, bucko. My fam's been in the assassination business for generations. Sounds ridiculous, right? But nope, it's all true. Mom and Dad are both assassins, and my big sis's an intermediary who takes murder requests. She's the one who got me this job,” she explained in a high-pitched voice. “The client was a young woman who'd survived a mass suicide. She gathered in an abandoned house as part of a group of seven people who'd met online. They'd planned to all die, but as they talked about their lives, they realized that they each had someone else they hated enough to kill. So they decided to hire a murder agency. I mean, they were going to die anyway, so might as well go out with a bang, right? But man, if they wanted to die that badly, why didn't they let me kill them myself?”
The woman facing Riria took an object from her pocket. Even though they were meeting face to face, Riria was wearing a cat mask that she'd bought at a food stall, so the woman shouldn't have realized she was talking to the famous actress Riria Hasemi.
What she'd taken out was a deck of cards. As soon as she saw them, Riria realized what they meant. “That's...” she said, and the woman nodded, said “Yes,” and told the following story.
“One of the seven who'd gathered to commit suicide brought it. He was a young man. I don't know his exact age, but he was young enough that I'd still consider him a boy. His father had died five years ago. It seems these cards were found among his belongings.”
Riria tilted her head behind her cat mask.
“Was his father the culprit of the Playing Card Serial Murder Case?”
“Yes, that was how he interpreted it,” the woman said. “The boy then researched the incident, and realized that the case his father had committed, whether intentionally or by chance, followed the pattern of the Ten Commandments. He must have been a sharp kid. And as we talked, we realized something else: everyone there had someone we hated so much we wanted to kill them, who also lined up with the Ten Commandments. Isn't it surprising? That all seven of us had someone we hated?”
The woman's eyes began to shine with the light of insanity.
“So naturally, we started talking. 'Let's kill them all and make it look like the Ten Commandments'. We'd prepared a number of glasses of poison equal to the number of people there. But one of them wasn't really poisoned. It just had a sleeping pill. Do you know what that means?”
The woman spoke triumphantly.
“It means only one of us would survive.”
That made sense to Riria.
“And I'm the one who took that pill.”
That also made sense to Riria.
The woman shrugged slightly.
“It's all such a mess,” she said. “We were all going to die together in peace, but here I am, still alive, drinking coffee in a shithole like this.”
“Isn't that good, though?” Riria asked. “Life is precious.”
The woman chuckled.
“You think so?”
Riria shifted the corner of her mask and took a sip of her coffee. It was bad. Well, she did make it herself. Apparently, she was lousy at making coffee.
Or rather, there's only one thing she was good at.
That is... making locked rooms.
“Anyway,
I survived,” the woman said. “That's why I came to see you.”
The
woman pointed at Riria's face.
“To see you, 'Locked Room User'.”
When I heard Riria's story, the first thing that struck me as odd was the number of people. Riria had killed five people in this incident, including the body found in the hidden room. That was two short of the number of victims the woman had requested. Did that mean she hadn't managed to complete her assignment yet?”
“No, the murdering is all done,” Riria said, shaking her head. “Or rather, it was coincidentally done for me. I actually was originally planning on killing two more people. I prepared locked room tricks and everything, y'know? But I didn't wind up needing them. You know why? Because they died. Before they even set foot in the hotel.”
I was confused. They died before they reached the hotel? What did that mean?
But it seemed things had just clicked for someone else. Surprisingly, it was Miss Meirozaka who cocked her head and asked,
“Are you talking about the bus accident?”
Her words jostled a memory loose. It had been on the news in the lobby on the first night. A bus accident. Miss Meirozaka had said that the two victims who'd died in the accident were supposed to be guests at this hotel.
“Yeah, that's right. They died in that accident,” Riria said with a shrug. “I was really surprised, I didn't expect something like that would happen. So in reality, the plan to make the murders follow Knox's Ten Commandments was doomed from the start. You get it, right? Of the targets I called to the hotel, two of them died without me being able to do a thing. Let's be real, the whole thing was doomed from that moment. I tried thinking of ways to trick you all, but when it was all over, I'd still have two cards left. It's not a good look.”
Hearing Riria's words, Fenrir raised a hand. “Actually, I have another question about that.”
The look on Fenrir's face was strange.
“Isn't that story strange? Didn't the client say that the seven victims corresponded to Knox's Ten Commandments? But other than Mr. Sagurioka, who is a detective, and Ms. Shihai, who has a twin sister... What about Mr. Kanzaki, who arrived at the hotel late, and Mr. Shinkawa, who was found in the hidden room? The reason why those two conformed to the Ten Commandments was because you, Miss Riria, intentionally created the situation. Isn't that contradictory? It clearly contradicts your claim that your female client told you to kill them because they already followed the Ten Commandments.”
“Yeah, that bothered me, too,” Riria nodded. “I made various adjustments like making Kanzaki arrive late, but to be honest, I don't understand why I had to do things like that. But the client was very particular. 'You have to kill them in accordance with the Ten Commandments.' She was obsessed with it. She thought that by killing them in accordance with the Ten Commandments, they would be judged by God for their sins.”
“God's judgment...” Mitsumura murmured.
“That's quite the declaration,” Dr. Ishikawa said with a dissonant smile. “Since she called it judgment, did it have to do with the grudges the seven of them held? In other words, the motive is closely related to Knox's Ten Commandments.”
“Honestly, I don't get that either. The client didn't tell me the motives. She just told me which card went with which victim,” Riria said. Then she laughed a bit and smiled. “The only one I know anything about is the motive behind killing Manei. I told Kuzushiro earlier that he was an idol otaku, but from what I've heard, he used to stalk a member of a certain unit. The idol was running away from him when she was hit by a car. If that really happened, then no wonder someone would want to rub that guy out.”
Mitsumura's eyes went wide. Then, as if to confirm something, she repeated the words “Mr. Manei was an idol otaku.” She started as though she'd been taken aback. “Could it be... Is that what she meant?” The surprised expression on her face quickly changed to one of regret, strong enough to make her grit her teeth.
“I'm so stupid... We've all made a huge mistake,” she said in a rare show of emotion. “This crime wasn't copying Knox's Ten Commandments.”
All eyes turned to face her. “What do you mean?” Yozuki asked. “Didn't the client tell Riria to kill them in line with Knox's Ten Commandments?”
“No, she didn't,” Mitsumura replied. “She never once said to make it look like Knox's Ten Commandments.”
“But-”
“I know she said the words 'Ten Commandments'. But I can assure you, even if her client told her to 'make it look like the Ten Commandments', she didn't say 'make it look like Knox's Ten Commandments'. I'm certain of it, because the Ten Commandments she was talking about weren't Knox's Ten Commandments, but something completely different.”
Yozuki tilted her head.
“Another set of Ten Commandments?”
“Yes.”
Mitsumura stroked her long black hair.
“The Ten Commandments of Moses.”
The Ten Commandments:
You shall have no other gods before Me.
You shall have no idols.
You shall not take the name of the Lord your God in vain.
Keep the Sabbath day holy.
Honor your father and your mother.
You shall not kill.
You shall not commit adultery.
You shall not steal.
You shall not bear false witness against your neighbor.
You shall not covet.
“The Ten Commandments of Moses,” I muttered. Then I stopped Mitsumura, saying “Wait a minute,” and took out my pen and notepad to write down the Ten Commandments as I remembered them. Everyone looked at it.
After confirming it, Mitsumura said “Let's go over the incidents so far.”
“First, at the scene of the first crime five years ago, the card left behind was a six. The victim, a former detective, had previously killed someone in an accident caused by distracted driving. This corresponds to the sixth commandment, 'You shall not kill.'”
“Next, the number left at the scene of the second incident was five. And the victim, a Chinese man, resented his father for his lack of academic background. That corresponds to the fifth commandment, 'Honor thy father.'”
“And the third case. The number left was four, and the victim was the president of a black company that overworked its employees. This corresponds to the fourth commandment, 'Keep the Sabbath day holy.' The Sabbath is Sunday, so the victim, who forced his employees to work around the clock, was violating the Sabbath.”
We followed the commandments on the notepad with our eyes. Certainly, everything made sense so far.
“Next is the fourth murder – Mr. Kanzaki, killed in this mansion,” Mitsumura said. “The card left at the scene was an ace – that is, one. And the first commandment is 'You shall have no other gods before Me.' The 'Me' in this case is the Christian God. Mr. Kanzaki, who was a priest of Tower of Dawn, violated this rule.”
“And the fifth murder... The victim was Ms. Shihai. Her number was ten, and the tenth commandment is 'You shall not covet.' I heard from Kuzushiro earlier that Ms. Shihai acquired this huge mansion by marrying a rich man for his money. Depending on your point of view, that could be considered 'coveting another's property'.”
“The sixth victim was Mr. Sagurioka, and the number on the card left at his scene was seven. The seventh commandment is 'You shall not commit adultery.” It seems Mr. Sagurioka's affair was once reported in a weekly magazine, so he violated it. Next is the sixth murder, when Mr. Manei was killed.”
“The number on the playing card was two, and the second commandment is 'You shall have no idols',” said Dr. Ishikawa. “But I don't really get it. I'd heard that Mr. Manei used to be a fortune teller. Did he also sell statues of Jesus and the Buddha?”
After hearing those words, I looked down at the second commandment written in my notebook. “You shall have no idols.” Idols...
Mitsumura spoke up.
“It's likely easier for an English speaker.”
Fenrir, the British girl, spoke up. “It most certainly is.”
In other words...
“Mr. Manei, the idol otaku, worshiped idols above all else. Therefore, he violated the second commandment. Not only that, he was likely killed for stalking an idol. Considering that, it's natural to think he was killed for 'idolatry'.”
Seven eighths of the incidents now conformed to the Ten Commandments. All that was left was the desiccated corpse in the hidden room.
“This one is easy,” Mitsumura said. “The card left at the scene was a three, and the third commandment is 'Do not take the name of the Lord in vain.' The victim, Mr. Shinkawa, was another member of Tower of Dawn. The 'Lord' referred to here is the Christian God, but in a broad interpretation, Mr. Shinkawa could have been said to have violated this commandment.”
All of the cards left at the scenes were now connected to the Ten Commandments. “What are the odds?” I muttered.
“How could something like this even happen?”
The victims, who were supposed to have been killed in accordance with Knox's Ten Commandments, also conformed to THE Ten Commandments.
“Yes, it was unexpected,” Mitsumura said with a sigh. “It was all because the three victims targeted by the culprit five years ago and some of the victims killed in this incident just so happened to fit with both Knox and Moses's Ten Commandments. A whim of fate. And it caused Riria to make a terrible mistake.”
Mitsumura casually shrugged her shoulders.
“Earlier, you said the plan was ruined because two of the targets died in a bus accident, didn't you, Miss Riria? But you were wrong. Your plan was ruined from the beginning. Miss Riria, it was doomed from the moment you spoke to your client.”
Mitsumura looked at Riria with eyes full of pity.
“It's a shame the culprit was so stupid. You should have used your brain and confirmed it first.”
I saw Riria's eyes go wide.
Her once confident face filled with shame.
Thus, the curtain fell on the serial murder case in the House of Snow. All four of the locked room murders committed were quite elaborate. “I” enjoyed watching them quite a bit. But they are just a prelude to the murder that “I” will commit.
“I” was very surprised. Just as “I” was feeling proud of myself for having come up with a plan for the perfect crime, something like this happened. As a result, “I” was forced to wait for the case to be resolved. “I” am glad that everything was solved peacefully.
Now then, let's begin the real show.
“I” will now begin my murderous plan. Of course, it is a locked room murder. It will be the most perfect locked room murder ever committed.
Everyone is asleep. “I” left my room. “I” headed towards them.
“I” hate them. “I” have to kill them.
Now, let “me” show you. A gift from “me” to you.
A true locked room trick.
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