Пандора
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No, the thief planted a nuclear mushroom on the maniac. The thief would reveal the murderer if he came to watch over the victim that night and could plant any kind of clue, no matter how complex. Or rather, no matter how easy.
I still think the clues aren't that complicated. And the fact that Kayla was killed when he remembered it is no coincidence (in my opinion).
Imaris already gave himself away on the first night. So, he was the one acting on the second night.