The Rolf family — Marian (Black), Ben (Reed), Davey (Lee H. Montgomery), and Aunt Elizabeth (Davis) — have rented an old, worn-down mansion from the creepy Allardyces, Arnold (Meredith) and Roz (Eileen Heckart). They've been told that the only condition to renting the house is that they must care for the elderly Mrs. Allardyce, a recluse who collects photographs.
Marian quickly warms up to the house and decides to take care of Mrs. Allardyce herself. However, things start going wrong almost immediately. Ben almost kills Davey while roughhousing in the pool, Marian's temper starts flaring at the mere criticism of the house or Mrs. Allardyce, and Ben starts having nightmares about the chauffeur from his mother's funeral. After Davey almost dies from carbon monoxide poisoning, Elizabeth starts getting suspicious about the house's nature, but dies from mysterious circumstances the next night.
Ben soon finds out that the house has the ability to regenerate whenever someone dies or has an injury. Realizing that the house is eventually going to kill them all, Ben tries to take Davey and flee, but the house, and Marian, won't let them get away so easily.
This movie contains examples of:
- Adaptational Alternate Ending: Ben and Davey's deaths differ in the transition from book to movie. In the book, Davey drowns in the swimming pool, pulled under by the force of the house. Ben dies by striking his head on the concrete while struggling against the house's will to keep him seated while Davey drowns.
- The Bad Guy Wins: Marian becomes the new Mrs. Allardyce, and her family all die trying to escape. The house gets a new lease on life and the opportunity for more victims.
- Dead All Along: Mrs. Allardyce.
- Downer Ending: Marian becomes the new Mrs. Allardyce, Ben and Davey are killed and the evil house rejuvenates itself, awaiting its next victims.
- Everything Trying to Kill You: The house itself will use any way to attempt to kill its victims.
- Extremely Dusty Home: The inside of the house is extremely dirty and neglected when the Rolfs get there, despite having four people living there previously.
- Haunted Hero: After moving into the house, Ben starts having nightmares about his mother's funeral and starts seeing the car and chauffeur from the funeral in both the driveway and in the house itself.
- Haunted House
- Hope Spot: Marian regains her sanity and agrees to move out of the house. But, at the last minute, she's drawn back in the house and ends up getting completely possessed by Mrs. Allardyce.
- Mummies at the Dinner Table: The Allardyces' keep their mother's spirit around so that she can possess the next potential victim, turning them literally into Mrs. Allardyce.
- Never Trust a Title: There are no literal offerings in the film, burnt or otherwise. The title comes from the "offerings" Marian makes of her attention to Mrs. Allardyce and the affection for her family. In the novel, she asks the presence in the house to take away her devotion to her family and "burn it out" of her.
- Shoot the Shaggy Dog: Despite their efforts, Ben and Davey are killed before they can escape the house. Not to mention the Allardyces wanted the deaths to occur just so they'd have a nice house again.
- Slasher Smile: The chauffeur.