Julia Lofting (Mia Farrow), her husband Magnus (Keir Dullea), and daughter Kate (Sophie Ward) eat breakfast and Kate starts to choke on an apple. When the apple refuses to dislodge, Julia reaches for a knife and tries to perform a tracheotomy on Kate as she bleeds to death.
Julia leaves her husband and moves to a new house. An upstairs room contains a child’s possessions. Julia finds a mechanical clown toy with sharp, clanking cymbals and accidentally cuts her finger on them. In the park, Julia thinks she sees Kate, but she disappears. Julia hears strange noises and thinks its her ex husband. Odd events in the house such as noises and appliances that turn on by themselves.Later, Julia sees the girl in the park, and finds a mutilated turtle and knife where she stood.
Magnus’ sister, Lily, asks Julia if friends can use her house to conduct a seance. The medium, explains that spirits need to control someone to carry out physical acts. During the seance, the medium becomes frightened and tells Julia to leave the house immediately. Moments later, one of Lily’s friends, Miss Pinner, falls down the stairs. While Julia is out, Magnus breaks in her house. He sees something and follows it to the basement. He dies after falling from the staircase – his throat cut on a broken bottle.
A neighbor tells Julia the house once belonged to Heather Rudge, who moved away after her daughter Olivia died. Julia visits Mrs. Fludd, the medium tells her she saw a boy in the park, bleeding to death. Julia finds an article about a boy, Geoffrey Braden, murdered in the park. Julia Geoffrey’s mother Mrs. Braden who says a vagrant was executed for the crime but other children in the park murdered her son. She says she and her companion have been following the lives of the children. She asks Julia to visit the remaining two, Captain Paul Winter and David Swift. Julia visits Swift, an alcoholic, who admits that Olivia had power over him and the other children. She made them each kill an animal, and watch as she murdered Geoffrey. He says he told only Mrs. Rudge.
That night, as she sleeps, a hand caresses Julia’s face. The phone rings Julia tries to answer it, a hand pushes hers away, causing her water glass to fall and break. Later, Swift is shown leaving his apartment. He slips on a broken bottle in the stairwell and he falls to his death.
Julia tells her friend, Mark (Tom Conti) what she has discovered but he doesn’t believe her. That evening, her heater won’t turn off. She tries to unplug it. Mark is electrocuted when a lamp falls into his bath. Julia visits Mrs. Rudge in a psychiatric home. Mrs. Rudge confesses that she killed Olivia after learning of the murder. As Julia rushes she looks over her shoulder at Mrs. Rudge, who sees Olivia’s eyes. Mrs. Rudge dies of a heart attack.
At home, Julia sees Olivia in the bathroom mirror, and in the living room on the floor playing with the clown toy. She takes it from her, offers her a hug and asks her to stay. Julia is seen bleeding to death, her throat apparently cut on the sharp edges of the cymbals. The film was originally released in England as Full Circle but fared poorly at the box office and was released in the United States in “1981, when it was unveiled under a new title (The Haunting of Julia) and still failed to find its audience.