Laura Burney appears to have an idyllic life and a happy marriage to Martin Burney, a successful Boston investment counselor, living in a luxurious home that overlooks the sea along Cape Cod. Beneath his charming, seemingly stylish exterior, however, lies a possessive and controlling partner who has subjected Laura to years of physical, emotional, and sexual abuse. Their marriage unfolds in a troubling pattern: bursts of intimidation and fear followed by sweet reconciliations where he showers her with flowers and gifts, masking the pain with superficially affectionate gestures.
Their world is disrupted when a neighbor, a doctor, invites them for an evening sail. Laura, who harbors a deep-seated fear of water and cannot swim, faces a terrifying test of courage as a severe storm suddenly erupts. On the rocking vessel, Martin and the doctor struggle to regain control, while Laura is swept overboard. A long Coast Guard search ensues, but Laura’s body is never found, and Martin is left grief-stricken and inconsolable, clinging to the belief that she has drowned.
The twist arrives when the audience learns that Laura is very much alive. After secretly learning to swim, she plans to fake her own death to escape Martin’s abuse. In the storm’s chaos, she leaps overboard, finds her way ashore, and returns home disguised and with a plan: she cuts her hair, wears a wig, flushes her wedding ring down the toilet, pockets her funds, and heads to a nearby bus station to start over.
Laura relocates to Cedar Falls, Iowa, and conceals a crucial deception: she has moved her blind, stroke-impaired mother, Chloe, to a nursing home while telling everyone that Chloe had died. Now living as a new person, she rents a house, finds work, and builds a life apart from the man she once married. Her neighbor, Ben Woodward, a young drama teacher, grows attracted to the new woman in town, though he senses there may be more to her past than she reveals. They share a pleasant first date, but a kiss reveals Laura’s unease, and she ultimately admits to Ben that she escaped a dangerous marriage.
News of Laura’s survival reaches Martin when he discovers that she had taken swimming lessons, a fact that hints she did not drown. His suspicions sharpen when he spots Laura’s wedding ring in the toilet, evidence that something about the earlier disappearance wasn’t as it seemed. He travels to Chloe’s nursing home, posing as a detective, while Laura—still living under her assumed identity—happens to be there in disguise as well, narrowly avoiding a direct confrontation. Martin tracks down Laura’s whereabouts and uncovers Ben as a new part of her life. He follows the couple to Laura’s new residence, then breaks in while Laura and Ben are away. He also stalks them during a carnival date, leaving careful clues that reflect his exacting, controlling nature—the towels aligned perfectly, the kitchen cabinets arranged just so.
The tension culminates when Martin confronts Laura at her home as Ben crashes the door in a dramatic intrusion. Ben fights to subdue Martin, who retaliates with force until Laura acts. She trips him with a knee to the groin, disarms him, and calls the police. Martin expects Laura to cry out for protection, to once again rely on others to shield her from harm, but she instead declares that she has killed an intruder and then shoots Martin three times in the chest. A final struggle ensues as Martin grabs hold of Laura by the hair and wrests the gun, but the weapon misfires. Wounded, Martin collapses, and death follows as Laura Burney and Ben Woodward embrace, waiting for the arrival of the authorities to bring the ordeal to an end.
