At the fourth scene, as I hardly need to explain, there was no message. There was no reason to leave one. B was presenting the Los Angeles BB Murder Cases to L as a case that could never be solved.
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That L could not solve.
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In other words, he had never prepared any clear solution to it— since the killer had committed suicide, disguised as the fourth victim, there was no longer a killer to catch, and no clues left to catch him with.
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Which is why the difficulty had escalated so dramatically from murder to murder. Particularly the message at the third scene, with its deliberate ambiguities—am. versus p.m., and room 1313 versus 404. So when no message was discovered at the fourth scene, Misora, and therefore L, would believe they had simply overlooked
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it. Something that should be there, but wasn’t—and it was a lot harder to discover something that wasn’t there than something that was. Especially if the missing thing had never been there in the first place-in that case, there was no way they would ever find it.
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But how would they prove it?
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A problem with no solution could only have one answer—that it could not be solved. But that answer conflicted with the fairness displayed in the first three murders. Which tied their hands. Unable to find something that wasn’t there, L would have to continue searching for B—who no longer existed. The metaphor of the gradually decreasing Wara Ningyo established from the beginning that there would be only four victims, so the lack of further murders would not lead to the conclusion that the killer had passed away. L would be left chasing after the mirage of the deceased B. L would be forever followed by the mirage of the deceased B. L would spend the rest of his life trembling in fear of B’s shadow.
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L would lose.
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B would win.
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B was the top, and L was the bottom—L would grovel at B’s feet.
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The copy would surpass the original.
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Or so he thought.
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In reality this did not happen, and the dizzying amount of time he had spent preparing for his crimes was all for nothing, destroyed, blown to smithereens—because he had focused all his energies on L, and never once viewed Naomi Misora as anything more than a pawn. All his attention was on the man behind her, and he never even saw Misora standing right in front of him. Even as he believed himself to be praising her skills, he ultimately underestimated her. She had done better than he expected—that very expression is, essentially, arrogant. If you ask me, even without Ryuzaki’s hints, she might well have deciphered the messages at almost the same speed.
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Naomi Misora.
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The key had been the locked rooms. The locked rooms. Ryuzaki had said over and over that there was no need to think about them, that the killer had probably just used a spare key, because even he knew that focusing on that point could mean trouble. Beyond Birthday had a fair idea where the weaknesses in his own plot lay.
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But those were weaknesses that would be forgotten once the fourth murder happened, and if he could just hold out till then, if he could just distract her until then... then B would have won. That Misora figured it out just before the fourth murder was complete can only be described as a stroke of good luck.
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At the first scene, and the second, and the third, the Wara Ningyo had been directly across from the door, and the dolls had been at the same height as the latch of the thumb turn lock—she had to notice both these things to figure it out. At the third murder scene the dolls had been counted along with the stuffed animals, which had seemed like a reasonable enough idea, but that was not their primary function. And their function as a metaphor for the victims was, again, not their true purpose.
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Specifically, let us look at how the locked rooms were created. The doors were locked with a thread.
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The thread from a needle and thread. Misora had suggested running a thread under the door, looping it around the latch, and pulling on the thread to make the latch turn. Ryuzaki had denied it, but it had been a close call. She had been so close, but with that method, the force would have been pulling in the room direction, applying pressure to the door itself rather than the latch. As Ryuzaki had explained, the only effect would have been to pull outward on a door that opened inward.
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But she had been very close.
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At what she believed to be a potential fourth crime scene, Misora had crouched down in front of the door, putting her line of sight at waist height, and looked at the opposite wall—and imagined there was a Wara Ningyo there. Pinned to the wall across from her. Of course, the doll had to be physically pinned to the wall. There was no way it could just float there on its own—that would be magic, a scene out of a horror movie. It had to have been pinned there— which means there had also been something pinning it there. The holes in the wall at each crime scene—without even looking at the photos of the dolls in her files, Naomi Misora was Japanese, she knew about them as part of her culture.
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Wara Ningyo had nails through them.
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Long, thin nails.
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And what mattered to the killer was not the doll itself. . .but the nail. The Wara Ningyo were nothing but a dramatic bit of misdirection. The shape of the nails.. the nail’s head. The thread went under the door, around the head of the nail, and from there over to the side wall, around another nail head, and finally back to the door itself, around the latch of the thumb turn lock—at the same height as the dolls.
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Obviously, this is a simplified description to make it easier to understand, and the operation was actually performed in reverse, starting at the lock, then going to the side wall, the opposite wall, and back under the door, but. . . essentially, the thread sketched a big triangle in the middle of the room.
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And if you pulled the string then...
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The latch of the thumb turn lock would turn.
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Click.
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Essentially, he used the nail heads as pulleys, turning the power vectors diagonally. To be even more accurate, the Wara Ningyo was not placed directly opposite the door, or directly opposite the thumb turn latch, but directly opposite the gap under the door. This method prevented the dynamic force applied to the thread to be dispersed by the door. The thread did not touch the door, but simply passed under it, heading directly for the nail in the Wara Ningyo opposite— and all the force applied was transmitted in that direction. Then the nail head acted like a pulley, turning the direction of the force twice, and leading it to the thumb turn latch. Once the door was locked, obviously, he then had to recover the thread, so he had to use a particularly long one doubled over on itself.. .which explanation is just a bonus at this stage. As soon as he was sure the door was locked, he let go of one end of the thread and pulled on the other, successfully gathering all the thread to his side of the door. Anyone could pull this off, as long as they used strong thread that wouldn’t break. If you have time, try it in your own room. As long as you are allowed to hammer nails into the walls.
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Despite this tedious explanation, the exact nature of the locked room trick is completely unimportant.
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Well... perhaps not completely, but to focus too much on the trick itself is to miss the real point. What really matters is that to pull this trick off, you need at least two dolls—because you need two nail head pulleys. At least two. One on the opposite wall and one on the side wall. Four dolls, three dolls, two dolls—the trick worked at the first three scenes. But at the fourth scene, where there was only one Wara Ningyo, the trick could not be used. With only one pulley opposite the door, the latch would not turn.
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The thread would not make a triangle, and would simply go over and come back in a straight line. So, as I have already mentioned, the final victim, Rue Ryuzaki, turned the thumb turn latch by hand. We only know that because the locked room trick was solved before the fourth murder took place—
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otherwise, the fact that the locked room had been created even with only one Wara Ningyo would simply have been dropped into the file with all the other data. The weakness in his plan would evaporate—as long as the locked room remained a mystery until the fourth murder, it would remain one forever.
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Naomi Misora was just in time.
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Ryuzaki himself had asked absently, “What for?” Why had the killer made a locked room that he did not need? That question. A game, for fun... a puzzle. Locked rooms were designed to make a murder look like a suicide... but in this case, the locked rooms existed to make the fourth death look like it wasn’t a suicide.