Who stole the Moonstone?

Franklin Blake unknowingly removes the Moonstone from Rachel’s room during an opium-induced trance on the night of her birthday. He is not conscious thief; Dr. Candy’s dose and Blake’s anxiety trigger somnambulism. Godfrey Ablewhite — engaged to Rachel for her money — follows Blake, takes the gem from his room, and conceals it until his death exposes the truth.

Collins clears Rachel, who saw Blake but refused to ruin him, and exonerates servants like Rosanna who suffered suspicion. Jennings’s re-enactment proves Blake’s state. The answer matters because the novel is about how theft happens without villainous intent and how respectability hides Ablewhite’s real crime.