| Director | Charles Guard, Thomas Guard |
|---|---|
| Genre | drama film, horror film, mystery film |
| Runtime | 87 min |
| Country | Canada, Germany, United States |
| Box office | $42.7 million |
Following a suicide attempt after her terminally ill mother died in a house fire, Anna Ivers is discharged from a psychiatric institution after ten months; she has no memory of the actual fire, though recurring nightmares from that night frequently plague her. Back at home, Anna reunites with her older sister Alex and learns their father Steven has a new girlfriend, Rachel Summers, who was their mother's live-in nurse.
Anna and Alex become convinced that Anna's nightmares are messages from their mother, telling them that Rachel murdered her so she could be with Steven. The girls remain angry at Steven for moving their mother into the boathouse when she got sick, her only way of calling for help being a bell that Rachel tied to her wrist. Anna meets up with her old boyfriend Matt, who tells her he saw what happened the night her mother died, but Rachel intervenes before he can explain further.
Anna goes with Rachel into town so Alex can look through Rachel's possessions and Anna can talk to Matt again. The two secretly plan to meet that night, but Matt fails to show up. Anna has a ghastly hallucination of him; the next morning, his dead body is pulled out of the water, his back broken. The police state he fell from his boat and drowned.
After the sisters are unable to find any record of Rachel with the State Nursing Association, they conclude she is actually Mildred Kemp, a nanny who killed the children she was caring for after she became obsessed with their widowed father. While Steven is away on business, the girls try to gather evidence against Rachel to show the police, but Rachel catches them and sedates Alex. Anna escapes and goes to the local police station, but they disbelieve her and eventually call Rachel to take her home.
Rachel sedates Anna and puts her to bed; Anna sees Alex in the doorway with a knife before passing out. When she wakes up, she finds that Alex has killed Rachel and thrown her body in a dumpster in their backyard. When Steven arrives home, Anna explains that Rachel tried to murder them and Alex saved them. Confused and panicked, Steven reveals that Alex died in the fire along with their mother. Anna looks down to find that the bloody knife is in her hand, then finally remembers what happened on the night of the fire. After catching Steven and Rachel having sex, she became enraged, filled a watering can from a gasoline tank in the boathouse, and carried it toward the house, intending to burn it down. However, she failed to close the faucet and it spilled a trail of gasoline that ignited when a lantern fell. Her mother was killed in the resulting explosion, as was Alex.
It is revealed that Anna has symptoms of both severe schizophrenia and dissociative identity disorder. Flashbacks reveal that Anna has been hallucinating Alex since she returned home from the institution, which is why no one else ever responded to Alex's presence or speech, only Anna's. She also remembers killing Matt at their planned meeting by letting him fall off a cliff and breaking his back after he revealed that he saw what she had done. She finally remembers killing Rachel, who was not a murderer, but a kind woman trying to make the family work, mistakenly perceiving her to be homicidal and callous.
The next morning as Anna is arrested for murder, the police question Steven, who reveals that Rachel's real name was Rachel Worshinsky; she changed her last name three years earlier to escape from her abusive ex-boyfriend. When Anna returns to the mental institution, she is welcomed back by the patient in the room across from hers, whose nameplate reveals she is the real Mildred Kemp.