Traitor.

The word blazed across Naegi's mind, a name that had become uglier to him than the worst insults he'd heard before entering Hope's Peak. Loyalty and trust were so hard to maintain here in the middle of the mastermind's game, where they were all supposed to be pitted against one another — and suspicion of a traitor could destroy the fragile bonds everyone had built. He could still feel echoes of the icy fear that had gripped the students in the wake of Ogami's exposure, turning friendship to ashes.

Four people had died because of what revealing one traitor had done to their ability to trust one another. How much more could be destroyed now, if they all started wondering whether Ogami had been the only one?

But on the other hand, the word might have meant something else — something no less dangerous, for all that the threat came from another direction. Traitor, the sign had said… and Ikusaba had offered to betray the mastermind to help them escape. Was it possible that the mastermind had discovered her change of heart, and that this had been some elaborate plan to eliminate her? Had the sign been meant to warn them all that this was how the mastermind dealt with betrayal?

But… Naegi's eyes went back to the knife, still plunged through the blackened corpse's chest. "How did they do it?"

"What are you talking about?" Togami demanded. "Do what?"

"Leave a message for us," Naegi said, frowning. "I mean… they can't have done it from a distance, right? Whoever did this would have had to be right here in the room."

"Yes?" Then Togami blinked, and his frown deepened. "Yes… that's true. This room was full of chemicals strong enough to knock someone out fast when I was here before — and the knife was definitely already there. I suppose someone could have stabbed her quickly, especially if she'd already fallen unconscious… but they couldn't have rigged that bomb trap in the few seconds they'd have left. Not unless they had some kind of edge the rest of us don't."

"Like an antidote?" Naegi asked dubiously. "Are there antidotes for knockout gases?"

"There are neutralizing agents," Togami said. "But those tend to diffuse over large areas. For a single person, the best solution would be a gas mask." He crossed his arms, scowling down at the body. "And if I were going to release a bunch of potential murderers into a building armed with poison gas, I would make sure that anyone on my side had a way to get around that weapon."

"You think there might have been a gas mask in the school after all?" Naegi asked, considering the possibility. He supposed it might make sense for Ikusaba to have one, just in case something went wrong… but he wasn't entirely sure what Ikusaba was really supposed to do in the school, other than possibly operating Monokuma. There really wasn't a way to judge what kind of equipment she might have had on hand.

"I wouldn't be surprised to find one lying around somewhere," Togami said. "After all, there are still some areas of the school we haven't been able to explore yet."

That was true — they might have run out of staircases after reaching the fifth floor, but there were still all too many hidden areas scattered through the school. Naegi's thoughts turned immediately to the locked doors on the fourth floor, the fifth floor, and the dorms — the areas he'd been checking on his upgraded e-handbook map ever since Kirigiri had disappeared. Ikusaba had claimed that she would let Kirigiri explore one of those locked areas… which would have given both girls access to anything that might have been meant to stay hidden from the students.

Assuming that Ikusaba had kept her promise, of course. Togami had been pretty certain it sounded like a trap, rather than a genuine offer. And considering that Kirigiri had never returned from her exploration… well, this situation really eliminated a lot of the reasons why she might not have come back.

Two missing girls — well, technically three, but Jill didn't seem to fit into it. They'd all seen her bare hands often enough to know that she didn't have a tattoo, and however much this body had been brutalized, nothing about it resembled her scissors and crucifixions. So the options were two girls, one corpse… and one culprit. Naegi didn't like the conclusions that train of thought led towards at all.

He shook his head. "We don't really know if anyone really went into those areas, or if they even could. We're still just guessing."

"Not quite," Togami said. "There's one inaccessible room that we know someone's been inside — one that's very conveniently been sealed up again so the rest of us can't get a look of our own."

Naegi's eyes widened. "The headmaster's office?"

That's right… now that he thought about it, both Kirigiri and Ikusaba had definitely been in that room. Of course, Kirigiri hadn't said anything about finding new tools in there — but if she hadn't needed his help with anything that she'd found, she would have kept her mouth shut. In some ways, Kirigiri could be even more paranoid and distrustful than Togami at his worst.

But… that didn't make sense, did it? Naegi frowned at Togami. "Why would there be a gas mask in the headmaster's office?"

"It's as good a place as any," Togami said, shrugging. "If you're going to hide a cache of tools where you don't want students to get at them, why not put them in a place students would typically have no business going?"

"Except that we all wanted to get in there as soon as we saw the name," Naegi reminded him. He smiled a little at the memory of exploring the fourth floor with Togami, before the other students had forced them apart. Naegi would have checked every room as he came to it, but Togami had dismissed the identical classrooms out of hand, heading for the room with the most obviously useful label — and then he'd been so outraged at being denied entry. "That was why Monokuma had to make the new rule about locked doors, remember? We were all talking about breaking it down to explore the headmaster's office."

"Which means there must have been something important in there," Togami said, his eyes narrowing again with echoes of his earlier frustration. "I shouldn't have hesitated — I should have found a way to break down that door before he had a chance to make that stupid rule."

"I don't think he'd have let you," Naegi said. "I mean, he keeps calling himself the headmaster, so…"

He trailed to a halt as his own words caught up with him. Monokuma always called himself the headmaster. But if Ikusaba was the one operating Monokuma, that wouldn't make sense. How could a girl their own age, one that Kirigiri and Ogami had both referred to as the sixteenth student, be the headmaster?

But… Kirigiri hadn't said that Ikusaba operated Monokuma all the time. In fact, she'd said the opposite — that had been why she'd needed Naegi to distract Monokuma while she snuck away to meet Ikusaba. That all might have been part of Ikusaba's trap, of course… except for one thing.

"Alter Ego," Naegi said slowly, his thoughts swirling so madly through his head that it seemed to take an age to piece them together into real sentences. "Alter Ego said the headmaster was here in the school, too."