In a decaying mansion, the Merrye family suffers from a rare genetic disorder causing them to mentally regress as they age. The three Merrye children, Elizabeth, Virginia, and Ralph, are under the care of the loyal family chauffeur, Bruno. The children exhibit increasingly disturbing and violent behavior due to their condition. One day, distant relatives Emily and Peter arrive with their lawyer, hoping to gain control of the Merrye estate. Their intrusion threatens to disrupt Bruno’s vigilant care and provoke the erratic and dangerous tendencies of the children.

As the relatives negotiate their stay, the situation spirals into chaos, marked by macabre and darkly comedic episodes. Bruno struggles to keep the violent impulses of Elizabeth and Virginia in check, while Ralph's animalistic behavior escalates. Emily insists on uncovering the secrets of the Merrye household, oblivious to the peril she faces. The chilling atmosphere heightens as night falls, leading to a series of bizarre and terrifying events.