Cyrus West’s greedy relatives eagerly await his inheritance, only to learn his will is set to be read 20 years after his death. When the day arrives, they gather at his dark mansion. The will reveals that Annabelle West, his only namesake heir, inherits everything—provided she’s deemed sane. If not, the inheritance goes to a mystery person named in a sealed envelope. But before Mr. Crosby, the lawyer, can disclose this backup heir, he vanishes, kicking off a series of eerie incidents suggesting Annabelle might indeed be unstable.