The Keeper plot
"Christopher Lee, master of the macabre, takes you and his patients to the brink of insanity."
The director of the mental asylum Underwood is treating patients from the wealthiest families in British Columbia. The rest of the family members have died under mysterious circumstances, so someone hires a private detective, who puts his assistant in the building and passes her off as his niece. He claims that she comes from a family where the parents were all blood relatives and that they decided to keep their love platonic for genetic reasons.