Given the task definition and input, reply with output. In this task, you're given passages that contain mentions of names of people, places, or things. Some of these mentions refer to the same person, place, or thing. Your job is to write questions that evaluate one's understanding of such references. Good questions are expected to link pronouns (she, her, him, his, their, etc.) or other mentions to people, places, or things to which they may refer. Do not ask questions that can be answered correctly without understanding the paragraph or having multiple answers. Avoid questions that do not link phrases referring to the same entity. For each of your questions, the answer should be one or more phrases in the paragraph, and it should be unambiguous.

Passage: So Dark the Night is the story of a detective, Henri Cassin from Paris, who, while on a long overdue vacation, falls in love with innkeeper Pierre Michaud's daughter Nanette. She is a country girl with a jealous boyfriend. Nonetheless, the detective becomes engaged to her. Then, the night of her engagement party, the girl vanishes and later turns up dead. Cassin believes that the obvious suspect is Leon, the old boyfriend, but soon he is also found killed. Soon after Mama receives a warning that she will be the next to die, she is found strangled.
Pierre, fearing for his safety, decides to sell the inn. Henri returns to Paris and, because of his investigative skill, he is able to come up with a sketch of the killer by expanding and elaborating on information provided by a footprint found beside Leon's body.
To Henri's astonishment, the sketch bears the exact likeness of himself, and when he fits his shoe into the footprint, he realizes that he is undoubtedly the killer. After making a full confession to the police commissioner, Henri is evaluated by a psychiatrist, who determines that he is schizophrenic. Though placed under watch of a guard, Henri escapes back to St. Margot, where he tries to strangle Pierre. However, the police commissioner, who has followed Henri to the village, catches the detective in the act and shoots him.
Who vanishes and turns up dead?