In Cape Cod, Massachusetts, Laura Burney struggles to please her abusive husband, Martin, whose behavior ranges from patronizing and controlling to brutally violent. Laura is expected to dress and keep their beachfront home according to Martin’s liking, even arranging the bathroom towels in a specific order. One day, on the beach, Martin introduces himself to Dr. John Fleishman, a new neighbor working on his sailboat. Fleishman compliments Martin’s house and beautiful wife, remarking that he has noticed Laura staring out the window. Fleishman invites the Burneys to go sailing that night. Martin explains that Laura is afraid of boats, as she cannot swim and nearly drowned as a child, but promises he will try to persuade her to come. Back inside, Martin accuses Laura of having an affair with Fleishman, and beats her to the ground. When Martin goes into town, Laura walks to the beach and throws rocks at the lamppost nearest their house, shattering the light bulbs. Martin returns home, apologizes, and gives Laura a red negligee as a gift. He takes off her clothes and dresses her in the negligee, then plays an audio cassette tape of Hector Berlioz’s “Symphonie fantastique,” the same classical music he plays anytime he wants to have sex. Laura pretends to enjoy their lovemaking. Afterward, at lunch, she says has been offered a full-time job at the library where she volunteers, but Martin forbids her taking it. He reminds her of a time six months ago when she abandoned her housekeeping duties and disappeared for two days. Laura argues that her absence was justified, as her mother had just died and she had gone to bury her; nevertheless, Martin punished her with beatings. Martin suspects Laura is trying to incite a quarrel so she won’t have to sail with him that night, but he insists on her going. Later, they join Dr. Fleishman on his boat. Bad weather cuts the trip short, and Fleishman turns the boat around. As the sea becomes increasingly choppy, Martin loses his grip on the jib. He and Fleishman struggle to gain control of the boat, and Martin is thrown overboard. When he climbs back on, Laura is gone. In a panic, Martin contacts the Coast Guard. Meanwhile, Laura, who has secretly learned to swim, uses the broken lamppost to guide her home. She grabs a bag packed with clothes and cash, dons a wig, and flushes her wedding ring down the toilet. After cleaning up her tracks with a towel, she boards a bus to Iowa, and settles in the small town of Cedar Falls, where she rents a quaint house and fixes it up. Still frightened that Martin could track her down, she reacts skittishly to abrupt noises and movements. She meets her neighbor, Ben, an attractive drama professor who invites her to dinner. When he asks her name, she tells him it is “Sara Waters.” Ben notices a wound on Laura’s hairline, from Martin’s latest beating, and detects her skepticism when he offers to help get her a job at the local college. Regardless, he arranges for an interview, and Laura is hired to work at the library. She and Ben begin dating, and he slowly gains her trust. Eventually, she reveals that she came to Cedar Falls to escape her abusive husband. She also confesses that her mother, Chloe, who is blind, lives in a nursing home nearby. However, Laura fears it is not safe to visit her yet. Meanwhile, after holding a memorial service for Laura, Martin receives a phone call from one of her friends at the YWCA. The woman offers her condolences and inadvertently reveals that Laura was taking swimming lessons. In a rage, Martin goes to the beach house and discovers Laura’s wedding ring in the toilet. Realizing she is still alive, he goes to the nursing home where Laura’s mother, Chloe, once lived, in search of clues. There, he is shocked to discover that Chloe never died, but was moved to another facility. Using a private detective, Martin locates Chloe’s new nursing home and begins stalking her there. Ben helps Laura disguise herself as a man so that she can visit her mother. At the nursing home, Martin passes Laura in the hallway but does not recognize her. Laura has a tearful reunion with Chloe, and reveals that she left Martin. She also tells her about her new relationship with Ben. Soon after, a receptionist alerts Martin that Chloe had a guest. Posing as a police officer, he convinces the blind Chloe that Laura is in danger. Chloe gives him the only information she can recall from Laura’s visit, citing her daughter’s new relationship with Ben, a college professor in Cedar Falls. Martin stalks Ben and Laura at a fair, then follows them home. While Ben sets up a picnic in his backyard, Laura goes next door to change. Noticing the towels in her bathroom are arranged the way Martin liked them, she searches the house in fear, but finds no one. After the picnic, Ben and Laura kiss goodnight. Laura returns home to find her bathtub overflowing. She discovers her pantry has been reorganized, and panics. Berlioz’s “Symphonie Fantastique” plays on her stereo, and Martin appears with a gun as Laura tries to escape. Ben knocks on the door, and Martin points the gun at Laura’s head. She peeks outside and tells Ben to go away. Sensing something wrong, Ben breaks in and tussles with Martin, who easily overpowers him, knocking him unconscious. Martin presents Laura with her old wedding ring. Instead of taking it, she knees him in the groin and steals his gun. Although Martin does not believe she can harm him, Laura trains the gun on him, calls police, and informs them she just shot an intruder. Hanging up the phone, she shoots Martin three times. He collapses, and she cries over his body. Martin revives and retrieves the gun, but it is empty when he pulls the trigger. As Martin dies, Laura rushes to Ben’s side, and the two embrace.