[Ttak]

Originally Posted by Hareoic

Spoiler for Longshot theory about Rosa and the chapel:

Suppose it was sleeping drugs that made it possible for the culprit to murder everyone in the chapel. They might need a scapegoat if they couldn't pull off blaming it on the witch. Thus, they let Rosa go and she forgot it as though it were a dream.

But we can say too that Rosa wasn't on the chapel. I don't trust too much on that scene, specially because of everyone acknowledging Beatrice. At least the culprit and the six parents were there at the time of the murders and, as said before, the theory about a trap X wasn't denied with the red text. The culprit could've given the letter to Maria but with a fake key, then, after closing the chapel with the real key, delivered the real envelope + key to Maria.