20 years after Cyrus West's death, family members gather at his mansion for a reading of the will. Laura La Plante, who stars as Cyrus' niece Annabelle, learns that she is the only beneficiary of her uncle's will. The catch? A doctor must declare her sane in order to receive the fortne. As luck would have it, an escaped mental patient who thinks he's a cat, has taken refuge in the mansion, planning to rip apart his victims as a cat would a canary.