Chapter 5: Unraveling the Main Trick
They were beginning the deduction show... Yozuki was told as much and summoned to the specified location: Kuzushiro's cottage. Besides Kuzushiro, Mitsumura and Chiyori Kurokawa were there, too. They said they were going to solve the trick behind Ms. Breakfast's locked cottage. The role of detective was being played by Kuzushiro.
But...
“Why is the deduction show being held at Kasumi's cottage?”
Wouldn't it have made more sense to hold it in Ms. Breakfast's cottage where the crime had taken place? That's what Yozuki thought.
“There are unavoidable circumstances.”
Kuzushiro said so. So, there were unavoidable circumstances. Well, then, let's see. What were those unavoidable circumstances?
“Let's demonstrate the trick, then,” said Kuzushiro. “Please step outside for now.”
“What? But I just got here!” Yozuki said.
“I have some preparations to make.”
“Please finish your preparations before I get here...”
“Well, I guess that's fair.”
But he still kicked her out of the cottage. He even instructed her to take a walk around. So, Yozuki, Mitsumura, and Chiyori Kurokawa did take a walk around. Killing time while someone prepared a locked room trick – this was, without doubt, the world's most unusual girls' night out.
After about five minutes of walking, they returned to the cottage to find Kuzushiro waiting outside the front door. She asked “Kasumi, were you able to create the locked room?” and he answered “Yes, I was.” It reminded her of when they used to play hide and seek as kids. How nostalgic. Yozuki went up to the door and tugged on the doorknob. She heard the deadbolt catch.
“Good job, you locked it properly.”
Then Chiyori Kurokawa asked “Where are the key cards to this cottage now?”
Hearing that, Yozuki thought that Chiyori Kurokawa didn't know the trick any more than she did. Judging from the look on her face, it appeared Mitsumura did. But she looked like she was judging Kuzushiro to see if he'd actually found the correct trick. “The key cards?” Kuzushiro said to Chiyori Kurokawa. “They're inside the cottage. Just like the real crime scene, it's a locked room. Take a look for yourself.”
Kuzushiro spoke like a great detective, circling the perimeter of the cottage and guiding Yozuki and the others to the cottage's window. The window of the cottage where Kuzushiro was staying was a double window just like the one at Ms. Breakfast's cottage, and like that window, it was locked with a crescent lock. Looking through the window, Yozuki saw a small Shiba Inu plush lying on the floor. She wondered where it had come from. Was that supposed to be the “corpse”? And there were two key cards lying next to it. Were those... the key cards to the cottage?
Yozuki nodded.
“It certainly is the same as the crime scene,” Yozuki said.
“That's only if those key cards are real,” said Chiyori Kurokawa.
Kuzushiro said “I agree,” and picked up a rock from next to the window.
“So let's go inside and see.”
With that, Kuzushiro broke the glass near the crescent lock with the rock in his hand. Even though it was his own cottage, he didn't hesitate to break in. Then he used the crescent lock to open the window and entered the room. Yozuki approached the plush Shiba serving as the corpse and picked up the two key cards that lay next to it. They certainly looked like real key cards. But to confirm if they actually were, Yozuki approached the cottage's front door. The door had a thumb turn, and it was set to be locked.
“It's locked properly.”
Chiyori Kurokawa checked the door herself over Yozuki's shoulder. “Hmm... So it is.” Yozuki unlocked the door and stepped outside. Chiyori Kurokawa, Kuzushiro, and Mitsumura – everyone – followed her. She shut the door behind them.
“If these two key cards are both real,” Yozuki said, staring at the key cards in her hand, “this is a real locked room.”
That would mean the mystery of Ms. Breakfast's locked cottage had been solved. Thinking about that made Yozuki nervous.
There was a sticker with a 4 on the key card, and a plate with the same number affixed to the door. So the numbers matched, but there was the possibility that the keys had been faked by sticking a sticker on a different key card. So the only way to confirm these were the actual key cards was to insert them into the card reader.
“Alright, then, here I go...”
Yozuki said as she inserted the first card into the card reader on the door. There was a beeping sound and the door locked. When the rattled the knob, it was properly locked.
“Looks like the first key card is real,” Chiyori Kurokawa said, raising an eyebrow. “What about the second?”
“I'm putting it in now.”
Yozuki inserted the second card key. She heard the beep again, and the sound of the deadbolt retracting. When she gave the doorknob a pull, the door swung right open. The door had been unlocked.
“...No way.”
The voice leaked out on its own. The cottage where Yozuki was staying also locked with a card reader, so it was easy to understand. The door didn't have an autolock, so just closing it wouldn't be enough to lock it. It could only be locked by inserting a card key, and it could only be unlocked by inserting a card key. In other words, if it could lock or unlock the door, the card key was genuine. And her experiment just now proved that both of the card keys in the cottage were genuine.
When Yozuki made a surprised expression...
“It looks like the experiment was a success.”
Kuzushiro had a smug look on his face. ...Yozuki was getting pissed off. He was totally taking advantage of things to get under her skin. Yozuki felt a strong desire to beat him to a pulp, but she swallowed the urge, swallowed her pride, and asked.
“What trick did you use?”
Kuzushiro put his hand in his pocket and said “The trick itself is simple.” Then, he took “it” out of his pocket and showed it to them.
“I locked the door with this.”
Yozuki and Chiyori Kurokawa's eyes widened. Because the item Kuzushiro held in his hand was...
The forbidden third key card.
“No, hold on a minute.”
Yozuki looked at her hands. There were still two key cards in them. However, there was a third one. Without hesitation, Kuzushiro inserted it into the card reader. There was a beep and the sound of the lock. Yozuki lunged at the doorknob to confirm it was locked. The door, which had definitely been unlocked just a moment ago, was now locked. What did that mean? She was so confused. Why...
“Why is there a third key card?”
After all, there should have only been two key cards. There were no other keys – that's what Hitsujiko had said. But now there was a third one... This was fraud... This was a complete violation of the rules!
“I can't just overlook this.”
Chiyori Kurokawa looked even angrier. What did this mean? She demanded and explanation and an apology. Depending on Kuzushiro's response, she may have kicked him where the sun didn't shine.
However, Kuzushiro responded like this:
“The third key card isn't all I have.”
With that, Kuzushiro pulled a new “it” from his pocket. “It” was another key card – a fourth key card that would send ripples through the mystery fandom.
Kuzushiro inserted it into the card reader. There was the beep and the lock. It was real. “Moreover,” he said.
“There's also a fifth key.”
There was even a fifth one? This was getting out of hand.
Yozuki's concerns fell on deaf ears, and Kuzushiro took out the next key card. He wasn't bluffing. He inserted it into the card reader. Beep, click. The door was once again unlocked.
Yozuki was a crucible of confusion. Or maybe a cruciferous vegetable of confusion. What... What the hell? Why did he have five key cards?
Yozuki spoke her mind.
“Kasumi, I hate you so much.”
Kuzushiro looked very sad. Had she gone too far? Mitsumura spoke, as if trying to help, “That isn't it, Yozuki. That isn't it.”
“As you know, there are only two key cards to the door to this cottage. The third, fourth, and fifth key cards don't actually exist. You question how he has them, but that's the exact point of the trick. Kuzushiro has increased the number of key cards.”
Yozuki was stunned for a moment. Then she asked a perfectly reasonable question.
“How did he do that?”
“Of course,” Mitsumura said,” by using the Infinite Key Duplication Trick he set up.”
“Huh? The Infinite Key Duplication Trick?”
She had no idea there was such a convenient trick! As Yozuki started getting excited, Mitsumura told her to calm down.
“So, with this trick, you could leave a theoretically infinite number of key cards inside the cottage. Ten, a hundred, even. And still have a card left to lock the door with.”
That was... ridiculous. What kind of trick would let you do something like that? Chiyori Kurokawa seemed to speak Yozuki's feelings.
“Of course that's not it,” she said, stroking her short hair. “No matter what trick you use, there's no way you could infinitely increase the number of uncopyable key cards. Therefore, the third, fourth, and fifth key cards Kasumi used are all fakes. In other words, the Infinite Key Duplication Trick is a trick that allows you to lock the door using a fake key. That's all.”
Hearing that, Kuzushiro and Mitsumura exchanged a look. After thinking for a moment, Mitsumura said “So you realized.” Kuzushiro shrugged and said “Indeed, it's just as Ms. Chiyori said...” and began to reveal the trick.
“The third through fifth key cards I used earlier are all fake. I just borrowed the key cards to some empty cottages from Ms. Hitsujiko and used the mansion's printer to print fake stickers to paste on them. To be precise, the second key card was also fake. In other words, one of the two key cards left at the scene is fake. Then, the culprit uses the second real card they took with them to lock the door, making the scene a locked room.”
Of the two key cards left at the scene, one of them was fake... That theory made sense. But the problems started here. How did they lock and unlock the doors with the fake key card? What kind of miraculous trick would make something like that possible?
Kuzushiro gave another shrug.
“Like all miracles, the actual operation is simple,” he said, as he put a hand in his pocket. “The card reader on the door... All I had to do was make one little addition.”
Kuzushiro took the item from his pocket and showed it to Yozuki and the others.
It was a long, slender pair of tweezers. Kuzushiro inserted the tip of the tweezers into the slit of the card reader. And he plucked something out of it. Yozuki looked at what was held in the tip of the tweezers. It was...
“A key card?”
Yozuki exclaimed. What was held in the pair of tweezers in Kuzushiro's hand was unmistakably a key card. No, to be more precise, it was a piece of a key card.
Yozuki tore her gaze away from the piece of key card in the tweezers and looked at the two key cards she held in her hands.
The key cards to the cottages were rectangles measuring 8 cm x 5 cm, and they were solid white, except for a 1 cm x 5 cm portion at the tip that was pitch black.
“The black part of the key card holds the magnetic data,” Kuzushiro explained. “That's the part the sensor inside card reader reads to lock or unlock the door. On the first day when we arrived on Wire Mesh Island, I had all that explained to me.”
And the object currently being held in the tweezers in Kuzushiro's hand was the pitch black magnetic end of the key card. The magnetic data of the key card had been separated from the rest and inserted into the card reader.
What would happen as a result? If the magnetic data of the key card was inserted into the reader, what would happen if a fake key card was inserted after it?
The answer was obvious.
The magnetic data would be pushed deeper into the card reader by the fake key card. If the card were as think as a business card, it might not be pushed properly, but since the key cards on the island were 2 mm thick, the magnetic data would be pushed in smoothly. Then, the magnetic data would be read by the sensor in the back of the reader, and the door would be locked or unlocked. In short, the door would unlock even if a fake key card was inserted into the reader.
Therefore, even if they left a fake key card at the
scene of the crime, that fake would still be able to lock or unlock
the door, and as a result, the fake key card would be recognized as
real. The culprit had set up the trick to force them to recognize a
fake key card as real.
“So you're saying,” Chiyori Kurokawa asked, “that the culprit took one of the two real key cards, cut off the black part, and inserted it into the card reader?”
“Yes, that's exactly it,” Kuzushiro said with a nod. “The black part of the key card is the main part, so to speak, and the rest is just decorative. In fact, when Mr. Shitsugi handed me my key card, he told me 'if that part gets scratched, you will no longer be able to use the key card. If it was anywhere else, there would be no problem no matter how bad the scratches were.' So you can just cut off the black part and use it on its own, and the functionality would be exactly the same.”
“But there is a problem with this trick. By cutting the key card and putting it in the reader, the culprit destroyed one of the two real key cards. The trick requires them to damage one of the real key cards. That's why the culprit took the key card off me when they attacked me. Of the two key cards I had on me, one of them was fake. Therefore, the culprit needed to dispose of that fake card before the police arrived. However, they didn't exchange that fake key card in my pocket for the real one. Mitsumura defined that as the mystery 'Why did the culprit steal the key card from Kuzushiro?' But now, the answer to that whydunit is obvious. It's because-”
“It's not that the culprit didn't exchange the key cards,” Chiyori Kurokawa said. “No matter how much they wanted to, they couldn't. Because the real key card no longer existed.”
The culprit cut up the real key card to use it for the trick. As a result, the “undamaged” key card was lost. That would certainly make it impossible to swap it back for the fake key card.
And that also made Yozuki realize what the “unavoidable circumstances” Kuzushiro had mentioned before starting the deduction were. If he'd demonstrated the trick at the actual crime scene, Ms. Breakfast's cottage, they would have had to damage the key card, an important piece of evidence, and the police would have yelled at them.
That's when Yozuki had a thought.
“Is the device in the card reader still there in Ms. Breakfast's cottage?”
If it was, they could have just used that for the demonstration.
Kuzushiro shook his head. “I just checked; it's already been removed.”
“The culprit probably retrieved the device right after they attacked me and took the fake key card. The device was designed to make people mistake the fake key card for the real one, so once they got it back, it no longer served a purpose. So it was best for them to collect it as soon as possible. Because if someone else found it before they did, they'd know in an instant what the trick was.”
Yozuki thought that made sense. But didn't that mean this trick was pretty risky? Until the culprit stole back the fake key card left at the crime scene, they couldn't recover the device they'd planted in the card reader. That was because if they inserted the fake key card into the reader after the device was retrieved, the reader would naturally reject it and the card would be exposed as a fake. So the culprit must have been sweating. The piece of the key card was deep in the reader, so unless someone deliberately looked inside, they wouldn't have found it. Still, with the murder investigation ongoing, there was no guarantee nobody would do exactly that. Although the risk was small, it wasn't zero. The culprit had gambled, and they'd won.
“Hmm, I see,” Yozuki said. It appeared this was the end of the explanations regarding the locked cottage. Yozuki asked Kuzushiro “Can I see that?”
Yozuki took the piece of key card from the tweezers in Kuzushiro's hand. When she looked closely, there were small springs attached to the side of the key card. They were right on the end of the black 1 cm x 5 cm section, three springs in total. Yozuki understood what they meant.
Cut off the black part of Key Card A (Henceforth, Black Card A) and put it into the card reader, then insert Key Card B. Black Card A would be pushed into the back of the reader by Key Card B, and the magnetic data of Black Card A would be read and lock the door. When you pulled out Key Card B, Black Card A, pushed deep into the receiver, would be pushed back a bit by the springs, and the magnetic data would no longer be seen by the sensor. From there, you could insert another card, Key Card C, and Black Card A would once again be pushed back and be read by the sensor.
“This resolves the mystery of the locked cottage,” said Mitsumura. “Let us now move on to the last remaining locked room, the locked Tower of the Cross.”
In order to explain the trick behind the locked Tower of the Cross, Mitsumura had us all go to Shitsugi's cottage. After all, how the key there could be taken from its locked room was probably the key to the final locked room.
However, en route to the cottage, Ms. Chiyori said “I just remembered I have to do something,” and walked off. Was there something more important than solving the locked room mystery? I wondered about that, but Ms. Chiyori disappeared without explaining herself further. How selfish... She really was a useless adult.
“Well then, I will now explain the trick.”
When we arrived at Shitsugi's cottage, Mitsumura
began speaking in her teacher voice. Her two students were myself and
Yozuki. Ms. Mitsumura stroked her black hair and began her lesson.
“As you all are already aware, the key to this locked room trick is this key: the one to the crime scene, the Tower of the Cross. Dr. Iori, who was supposed to have been imprisoned in the Tower of the Cross, was locked in that room, disappeared from the inside, and was replaced with the dead body of Mr. Gentleman. In other words, this is a trick that enables both disappearance and reappearance. To create this impossible situation, they needed the key to the Tower of the Cross to unlock the door. That's the only way they could have taken Dr. Iori from the room or placed Mr. Gentleman's body inside. However, the problem is how they got the key in the first place. Because that key...”
Mitsumura pointed to the door of the small room on the north wall of the cottage.
“As you know, it was kept in that room. And the key to that room was kept in a small safe, and to open the safe requires five keys. But there is no way to obtain the five keys needed to unlock the safe, as each key was kept by a different person. However, there is an addition wrinkle here: the sixth key.”
Yozuki had told me about it before we arrived at the cottage. If you had the sixth key, you could unlock the hidden second door on the back of the safe, so even if you didn't have all five keys, you could obtain the key to the room. However, the sixth key was...
“It was in the mansion, in a room being watched by as surveillance camera, right?”
That's what Yozuki had told me. But getting that sixth key would finally allow access to the Tower of the Cross. In other words, if you found out how to get the sixth key out of the room without being caught on the surveillance camera, you solved the locked room.
“No, that isn't it.”
Mitsumura completely rejected my idea. When I involuntarily went “Huh?” Mitsumura looked at me as though she couldn't understand my confusion.
“I mean, think about it. There's no way you could get the key out of the room without being caught on the surveillance camera.”
Yozuki and I were both taken aback. It was true that it seemed impossible to take the key out of the room without being seen on the security camera.
But what else could I have said... There must have been a way.
“But Mitsumura,” Yozuki said, unable to take it any longer. “You said it before. 'There's no way to take the key out of that room if you think about it normally'. That means if you think in a way other than normal, there is a way to get the key out of the room, right?”
Mitsumura looked surprised to hear that. Then she apologetically said “No, that's not what I meant at all.”
“No matter how you think about it, it's impossible, so let's just give up on finding a way. That's all I meant. I never thought you would interpret things like that, Yozuki. Japanese is a truly complicated language.”
“What the heck? Don't say such suggestive things, then!” Yozuki said angrily. “So what do we do? If we can't get the sixth key out of that room, we can't unlock the safe, right? And if we can't get the key to the room out of the safe, then we can't get the key to the Tower of the Cross from out of the room.”
She was right. No matter which way we looked, we were trapped. However, Mitsumura said something unexpected.
“They took the key to the Tower of the Cross out of the small room.”
Mitsumura spoke with cool eyes.
“All they had to do was use the key to the Tower of the Cross without taking it out of the room. That's the trick used in this case.”
“Unlock the Tower of the Cross without taking the key out of this room?”
I couldn't help myself. That statement was just absurd. Yozuki also had an uncomprehending look on her face and said “Eh? What do you mean?” Then she asked me for help.
“Kasumi, do you understand what Mitsumura is saying?”
“Nope, no idea.”
“So, we've finally pushed Mitsumura beyond her breaking point? She must have lied and said she's solved the locked room when she really hadn't.”
“There's a good chance that's what happened.”
“Yeah. I feel sorry for Mitsumura. We should have thought more about her mental state. All this could have been avoided...”
“You two know I can hear you?”
Mitsumura was glaring a hole right through us. Yozuki shuddered and quickly his behind me, shouting “It was Kasumi!” I was surrounded by nothing but terrible women. Seeing us like that, Mitsumura let out a big sigh.
“Well, anyway, let me explain how it was done. How the key to the Tower of the Cross was used without taking it out of that room.”
Mitsumura said that and approached the door of the small room on the north wall. Then she gave the doorknob a rattle.
“As you can see, the door to the room is currently locked. And inside the room is the key to the Tower of the Cross. Please take a look.”
The door had a peephole at eye level. When I looked into the room, I saw the key to the tower, hanging on its hook as usual, directly across from the door. The room was about 2 meters deep, meaning the distance between the door to the key was also about 2 meters.
“Well, first we have to collect the key.”
Mitsumura said that and moved over to the wall of the cottage. For some reason, there was a laundry pole propped up there. Had Mitsumura brought it? A wire was wrapped around the tip of the pole, bent into the shape of an L.
Mitsumura inserted the laundry pole with the wire through the peephole in the door. The pole was over 2 meters long. When she brought the L-shaped wire close to the key to the Tower of the Cross, she hooked the tip of the wire to the ring on the key's chain. If she lifted the pole upwards like that, the key would come off the hook on the wall, and the ring would catch on the end of the pole like a ring toss game. As she raised the tip of the laundry pole further, the ring slipped onto the pole and she withdrew it back to the door. The key to the Tower of the Cross was now just inside the door.
“Now, I can take the key to the Tower of the Cross in my hand,” Mitsumura said, sticking her right arm through the gap in the bars on the peephole. The gaps between the bars were each 10 cm square, more than enough to admit a human arm. Mitsumura grabbed the ring attached to the key with her right hand, then used her left to pull the laundry pole back through the door. Thus, Mitsumura held the key in her hand without having to enter the room.
But this was where the problems started.
Mitsumura tried to pull her right hand out of the gap in the iron bars, taking the key with her. But that was impossible. The key to the Tower of the Cross had a ring on the end of its keychain with a diameter of 20 cm. The gaps between the iron bars were 10 cm x 10 cm square, with diagonal lengths of about 14 cm. Therefore, there was no way to fit the ring through the gap in the iron bars, and the key attached to the ring couldn't be taken from the small room.
That fact had been verified countless times. But...
“There's no need to take the whole key out of the room.”
Mitsumura said that and picked up the key from the other end of the chain. Then, she pulled it and the ten centimeters of chain dangling behind it through the peephole. The ring got caught on the bars. But Mitsumura didn't pay it any mind and took a handkerchief from her pocket, which she used to tie the chain hanging halfway through the door to the bars.
“The preparations are now complete.”
I took another look at the door of the small room.
The key to the Tower of the Cross was hanging loosely from the peephole in the door. It couldn't fall back into the room because it was secured to the bars by the handkerchief. But I couldn't call this a complete trick. Since the ring on the keychain was stuck in the bars, it couldn't be taken from the cottage. That meant it couldn't be used. Therefore, it couldn't open the door to the Tower of the Cross. The locked room remained a locked room, never to be opened.
“You're right,” Mitsumura said, reading my mind. “Certainly, if we stop here, the door to the Tower of the Cross won't open. The impossible will remain impossible. But that's why tricks were invented. Making the impossible found at the crime scene possible... After all, that's what tricks were created for.”
So saying, Mitsumura raised her right hand.
“And now, the time has come to activate the locked Tower of the Cross's trick.”
She snapped the fingers of her right hand. And at that moment...
The ground shook.
It was an unexpected sudden earthquake. The floor of the cottage suddenly flew off balance and shook beneath our feet. It was as bad as an express train going at 80 kilometers per hour. I tried to grab onto something, but my hand grabbed only air and I fell to the floor. Yozuki also collapsed spectacularly. However, Mitsumura, who had anticipated the earthquake, remained on her feet, looking totally unfazed.
At that moment, I realized. Oh, this wasn't an earthquake. It was man made.
Look...
The cottage was flying.
When I looked out the window, I saw us gradually rising away from the scenery outside. It was a familiar view. I had seen something similar recently... No, yesterday.
The moment I realized that, I ran to the window on the south side and threw it open. Fortunately, the cottage had only risen about a meter off the ground. I jumped outside through the window. And when I looked back, I saw exactly what I'd suspected.
The crane...
The truck-mounted crane was holding the cottage on wires. The wires were tied to the four whisked decorations on the four corners of the roof. It reminded me of the view of the scene that had happened yesterday when that locked room trick was demonstrated.
That's right, this cottage could float... when it was lifted with a crane.
I approached the truck-mounted crane lifting the cottage. Ms. Chiyori was in the driver's seat. I called out to her.
“What are you doing, Ms. Chiyori?” I guessed she'd been recruited again.
“Can't be helped,” she said, pouting her lips. “It's not like I'm doing this because I want to.”
“No, I mean... Can you really drive that crane?”
“I'm a handy gal. I've got lots of qualifications.”
After Ms. Chiyori said that insincerely, she gestured for me to get back in the cottage. When I returned, it started rising again.
“But...” I said to Mitsumura. “What's the point? Lifting the cottage with the crane doesn't get us any closer to solving the locked room.”
It was an act that had no meaning. Why was Mitsumura doing it?
Mitsumura smiled slightly and said “You'll see soon enough.” Then she pulled a walkie-talkie from her pocket and said “Go ahead.” From the other end, Ms. Chiyori's voice replied “Roger.”
On that signal, the cottage shook again. When I looked out the window, the scenery was moving. I realized that the crane's truck had started driving with the cottage still raised.
The truck-mounted crane went out on the road and sped up. Yozuki sank to the floor and appeared to spend some time in a daze, but then, she appeared to notice something and pointed to the window. “Kasumi,” she said. And I saw what she meant.
The Tower of the Cross...
The huge cross-shaped building came into view. The truck-mounted crane was gradually approaching it. Through the cottage's double window, I could see the door of the right bar of the Tower of the Cross. It was the door to the room where Gentleman's corpse was discovered. The cottage, suspended from the crane, was approaching the door on the side of the tower head-on, in a direct line with the double window. Eventually, the right bar of the tower started approaching the window. If we kept going like that, it would be bad.
“We're going to hit it!”
As Yozuki and I panicked, Mitsumura casually approached the south-facing window and opened it wide. Then she quickly got out of the way. Yozuki and I also panicked and got as far away from that window as possible. All the while, the crane never even slowed down, and before long the cottage and the right bar of the cross were seconds away from collision.
“............Eh?”
However, the impact never came. Rather, something unbelievable happened. How on Earth? The right bar of the Tower of the Cross...
Entered the cottage.
Well, to be precise...
The right bar of the cross was sticking through the open south-facing window of the cottage. Like a square peg through a square hole.
“I see.” I finally understood what was going on. “The right bar of the Tower of the Cross is a rectangular room 3 meters wide, 3 meters long, and 10 meters deep. Which would make the area of the side view of the right bar a square with measurements of 3 meters. And the window of the cottage is about 4 meters long and wide.”
The double window consisted of two windows of 2 meters each. Therefore, the total width of the window was 4 meters. This was a floor to ceiling window, so the height was as tall as the cottage's ceiling, which was also about 4 meters.
“So, this double window is a square with sides of 4 meters, which is a meter larger in each direction than the right bar of the Tower of the Cross. That meant it could fit through the window.”
Mitsumura nodded at me. “Yes, that's correct. And the depth of the right bar of the cross – that is, the length it can be fit in, is about 10 meters, just as you said before. And in this cottage, from the south window to the north wall is only four meters...”
The truck-mounted crane slowly inched forward, and the right bar of the Tower of the Cross went further in. It slowly pushed its way into the cottage, and just as it was about to hit the wall, Mitsumura told the walkie-talkie “Stop.” The truck came to a stop. The distance between the north wall of the cottage and the right bar of the cross was only about ten centimeters. It was like snugly fitting into your space at the parking garage.
“Just like that,” Mitsumura said, stroking her black hair. “The length of the right bar of the Tower of the Cross is much longer than the length of the cottage, so it's possible to insert the right bar all the way into the cottage, resulting in this.”
Mitsumura's slender fingers pointed. I was astonished.
Because...
The right bar of the Tower of the Cross was almost touching the north wall of the cottage, which meant that the door on the right bar was also close to the north wall of the cottage, only about 10 cm away. And, on the wall that door was so near... What was there?
I didn't even need to say.
“It's the room.”
I still mumbled in shock. Because the right bar of the cross was jutting through the south window, the door to the tower and the door on the north wall were less than an arm's length apart. It was only 10 cm.
And hanging from the peephole of that door was the key to the Tower of the Cross, which Mitsumura had tied in place with a handkerchief earlier. The ring on the keychain was caught in the iron bars, so it couldn't be taken from that room. But the key and the 10 cm chain attached to it were hanging outside the door. After staring intently at the key for a moment, Mitsumura gave the following instruction over the walkie-talkie.
“It isn't high enough. Please raise it a bit.”
The cottage shook and raised slightly, as instructed.
Mitsumura nodded with satisfaction and picked up the key to the Tower of the Cross. The height of the keyhole and the height of the key were exactly matched.
Which is why they touched.
The key to the Tower of the Cross, still attached to the iron bars, reached the door to the Tower of the Cross.
As if to prove it, Mitsumura reached over and stuck the key into the keyhole with the chain sill tied to the iron bars by the handkerchief. It unlocked with a click. Then she gave another instruction into the walkie-talkie.
The crane started moving again, and the door that had been right up against the wall moved back away. There was now a gap of several meters between the wall and the door.
“Now we can open the door.”
As announced, Mitsumura opened the door. The interior of the Tower of the Cross appeared before us.
Mitsumura gave a gentle laugh.
“This is the trick behind the locked Tower of the Cross.”
I was amazed by the locked room trick I had just seen performed before my eyes. She actually unlocked the Tower of the Cross without taking the key out of the cottage. With that, it would be possible to take Dr. Iori out of the room she'd been imprisoned in, and to lock the door after killing Gentleman. All that was left to do was to untie the handkerchief holding the key on the bars and used the laundry pole to hook the key back on the wall at the back of the small room, and it would be like nothing had ever happened.
The specific steps taken by the culprit were probably something like this:
① Insert the right bar of the Tower of the Cross into the cottage, bringing the key to the tower up to the door.
② Pump sleeping gas into the cottage until it fills the area inside the Tower of the Cross, putting Dr. Iori inside to sleep.
③ Unlock the door of the Tower of the Cross and bring Dr. Iori into the cottage.
④ Remove the right bar of the Tower of the Cross from the cottage.
⑤ Lower the cottage and take Dr. Iori out of the cottage (outside).
⑥ Bring Gentleman, rendered unconscious with drugs, into the cottage.
⑦ Raise up the cottage with the crane.
⑧ Insert the right bar of the Tower of the Cross into the cottage, move Gentleman into the tower, and kill him.
⑨ Lock the door to the Tower of the Cross.
⑩ Remove the right bar of the Tower of the Cross from the cottage.
⑪ Use the crane to return the cottage to its original position.
⑫ Use the laundry pole to hang the key back on the wall of the small room.
I looked around the cottage again. There was no furniture of any kind. That was because when Shitsugi was murdered, the culprit removed all the furniture before tilting the cottage over. But that was also clearly beneficial to the trick of the locked Tower of the Cross. Since there was no furniture in the room, there was nothing in the way when the right bar entered through the window.
I also looked up at the ceiling. All of the lights were embedded inside. Since they weren't hanging, they also provided no obstacle when the right bar of the Tower of the Cross entered the room.
“But can this trick be performed by a single culprit?” Yozuki asked. “It seems like you'd need at least two people: One to drive the crane, and one to observe the positioning in the room like you did, Ms. Mitsumura.”
Yozuki said something smart. But Mitsumura replied “No, a single person can commit this crime.”
“All they'd have to do is place a wireless camera inside the cottage and observe the footage from inside the driver's seat of the truck. That would let them see the relative position of the door and the bar. I'm sure the culprit hung a rope ladder through the window in advance, and after inserting the right bar of the tower into the window, they climbed on up. The window's a square meter larger than the right bar of the tower, so even with the right bar inserted, there's still room for a person to go in or out, allowing the culprit to go inside and unlock the door to the Tower of the Cross like I just did. Afterwards, they climbed back down the rope ladder and returned to the truck, moved the cottage with the crane to create a space, and opened the door to the tower. That would allow them to commit the entire crime on their own.”
That would certainly make it possible to commit the crime. It seemed like it would take a lot of effort, though.
“Perhaps the culprit is the type who spares no effort when it comes to creating perfect locked rooms,” Mitsumura said. “Well, if it's them, I'm sure they could pull it off.”
When I heard her say that, I went “Oh?” It sounded like she knew who the culprit was. So when I asked her about it, Mitsumura went “Oh?” as well.
And with an expression of complete surprise, she said it.
“Maybe you haven't noticed yet? I thought for sure you would.”
Yozuki and I exchanged a look. I hadn't noticed a thing. Yozuki and I aren't the type to notice things.
Mitsumura sighed and said “I see.” Then she stroked her black hair and told us “It can't be helped, so I'll just tell you.”
“The culprit is Ms. Otomigawara. She is the culprit behind every locked room murder.”
Otomigawara was the Living Locked Room Library. I took a deep breath. At the same time, I thought she totally could have done it. She was enough of a locked room lover, and more importantly, she was a deranged young lady.
But...
“Of course, you have some basis for that, right?”
I asked just to be sure. I didn't think Mitsumura would go around making accusations just based off of intuition, but I did want to know what her reasoning was.
Mitsumura nodded.
“I have a reason, of course,” she said. “Around noon today, Kuzushiro was attacked by someone and had his key card stolen, right? That incident is the basis for my assumption that Ms. Otomigawara is the culprit.”
I gingerly placed a hand to the area of my head where the culprit had attacked me. A lump had formed. So Otomigawara was the one who'd hit me. But how could she have known that? When I asked,
“The logic is simple,” Mitsumura answered. “At that time, the culprit hit Kuzushiro in order to steal the key card from him – that is, to retrieve the fake key card they'd left at the scene. We all agree on that, right?”
“Well, yeah.”
We'd already drawn our conclusions on that front. “So,” Mitsumura continued.
“The culprit wanted the key card, so they targeted Kuzushiro. But isn't that strange? If the culprit wanted the key card, they should have targeted Yozuki, not Kuzushiro.”
I frowned. I didn't understand what she meant. Why would they have attacked Yozuki? I was the one with the key card.
Mitsumura admonished me to “Think about it carefully.”
“After Ms. Breakfast's body was found, Yozuki was the one to take the key cards that had fallen at the scene, right? So, everyone at the scene at the time saw that she was the one to hold the key cards. At the very least, they would have known that Kuzushiro didn't take them. There was also the possibility that she would have given them to myself or Ms. Kurokawa. But the culprit went so far as to attack Kuzushiro to get the key card. So unless we assume that the culprit was attacking random people and just hoping they got the correct person, the culprit must have had solid evidence that Kuzushiro was the one holding the key card. So, a question: Who here on this island had that evidence? In other words, who knew that Yozuki had given Kuzushiro the key card?”
I remembered.
When I had taken the key card from Yozuki, we were in the library of the mansion. The one's there were Yozuki, Mitsumura, and Otomigawara.
“In other words, apart from myself and Yozuki, Ms. Otomigawara is the only one who knew that Kuzushiro had the key card,” Mitsumura said. “So if someone other than Ms. Otomigawara were the culprit, they would have attacked Yozuki first, not Kuzushiro. But Yozuki wasn't attacked, was she. Ergo, the culprit is Ms. Otomigawara.”
Otomigawara said that she'd decided on the participants of the Locked Room Trick Game after consulting with an online friend calling himself the Lord of Locked Rooms. But since Otomigawara was herself the culprit, there probably was no such person. She'd done it all herself.
“But why did Ms. Otomigawara kill everyone?”
As soon as I asked that, I realized what a meaningless question it was. Otomigawara was the Living Locked Room Library – in other words, an assassin. She probably only carried out the murders because she was hired to. And if we wanted to find out who'd hired her, all we had to do was ask.
Mitsumura, Yozuki, Ms. Chiyori, and I returned to the mansion to search for Otomigawara. But we didn't find her. Instead, we found Ms. Hitsujiko, who we asked about her location.
After thinking for a moment, Ms. Hitsujiko said “Maybe she's in the Tower of Heaven.”
“The Tower of Heaven?” Yozuki tilted her head as she spoke.
“It's the tallest building on the island,” Ms. Hitsujiko replied.
At that moment, I remembered. I'd heard about it from Ms. Hitsujiko on the first day when I arrived on Wire Mesh Island. A tower 40 meters tall, event taller than the fence surrounding Wire Mesh Island, stood right next to the mansion.
Otomigawara's study was there, and that was her favorite room, where she often spent time. After hearing that, we headed for the Tower of Heaven with Ms. Hitsujiko. The Tower of Heaven was surrounded by a waist-high fence, and after stepping over it and walking about 30 more meters, we arrived at the entrance to the tower. When we entered the tower, we saw a spiral staircase before us. As we climbed the stairs, Ms. Hitsujiko explained to us.
“There's only one room in the Tower of Heaven, the study on the top floor. The entire rest of the tower is stairs.”
The stairs must have gone up ten stories. When we finally reached the top, there was a door. I was the first to arrive and threw it open.
And there, I saw the scene.
The inside of the room was wet with fresh blood, and in the center stood the headless body of Otomigawara.
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