Christina’s House(2000)

Christina (Allison Lange), her dad (John Savage) and brother move to a new house, to be near the mother, who is committed to an insane asylum. Christina hears strange noises, and is convinced someone else is in the house.  Other teenagers are murdered nearby, and the police begin to investigate.  The dad acts weird and perverted, and is the obvious suspect.

Howie, the handyman (Brad Rowe) who is repairing the house for them, is the killer.  He was an inmate in the same asylum as the mother.  The mother either brainwashed him or possessed him to do this.  

At the end, another inmate is being released from the asylum.  This inmate and the mother exchange a knowing look, indicating that this inmate will carry on with the mother’s work.