In a quiet suburban Utah home, Grady Edwards [Dylan Walsh] shaves his beard, dyes his hair, and removes his brown contact lenses, only to reveal a chilling truth: he has murdered his wife and three children. As investigators dig into the case, they uncover a disturbing pattern: a similar slaughter of another family in New Jersey, hinting at a calculated serial killer on the loose.
Susan Harding [Sela Ward], a recently divorced Oregon housewife, crosses paths with Grady in a grocery store. He introduces himself as David Harris and spins a story of loss, claiming his wife and daughter were killed in a car accident. Desperate for companionship, Susan rushes into an engagement, planning a wedding in less than six months, eagerly clinging to a fragile happiness.
Susan’s eldest son, Michael [Penn Badgley], returns from military school with a healthy dose of suspicion toward his mother’s new fiancé. Grady/David invites him downstairs, where he has secret cabinets and a veneer of bonding over tequila. Michael’s doubts surface when David slips up about the name of his supposed deceased daughter, exposing a dangerous pattern of deception.
The tension deepens when a neighbor mentions America’s Most Wanted—a profile of a killer who resembles David. In a fit of calculated violence, David infiltrates the neighbor’s home, pushes her down the basement stairs, and suffocates her, leaving Susan and Michael increasingly uneasy about what lies beneath the surface.
Jay, Susan’s ex-husband, confronts the danger head-on after witnessing David’s assault on Sean, Susan’s younger son. He warns Susan that she knows little about the man she’s about to marry. David’s stability frays further when he abandons a job with Susan’s sister Jackie—an act that avoids showing identification and raises more questions about his past.
The plot twists when Jay confronts David about a troubling lie concerning his college history. In a brutal act, David clubs Jay with a vase and suffocates him with a plastic bag, then uses Jay’s phone to send a misleading message to Michael suggesting the danger has passed.
Two weeks later, the neighbor’s body is discovered, and David feeds the family a story that rings hollow for Michael, who overhears a more candid exchange than what the others are hearing. As Michael’s girlfriend Kelly urges him toward college, his fixation on David’s inconsistent stories grows louder, tugging him toward the dangerous truth.
The suspense peaks when Jackie hires an investigator, and David intercepts her email, driving him to Jackie’s home where he drowns her in the pool. Fueled by a need to know what’s in the locked cabinets, Michael bravely breaks into the basement while Kelly acts as a lookout. There, he finds David’s body stored in a freezer, an awful confirmation of the family’s deepest fears.
David retaliates with a brutal assault: he knocks out Kelly and traps Michael in the basement. Susan, shaken and furious, confronts him, and in a tense exchange, he tries to assert his dominance by declaring he thought she could be “Mrs. Grady Edwards.” When Susan realizes the truth, she fights back, and in a desperate moment she stabs him in the neck with a shard of mirror, sending him tumbling into the tub where he appears to die.
Michael escapes the basement and reunites with Kelly in the house’s corridor, where they discover Susan in the hallway, convinced that the threat has ended. But David resurfaces, blocking their escape and driving the trio into the attic. A brutal rooftop struggle ensues, and all three fall from the height, leaving them unconscious on the ground below.
When Michael awakens, he learns he has been in a coma for a little over a month. David is alive again, having fled before the police arrived. The closing scene reveals David, now under a new name—Chris Ames—and working at a hardware store, where he calmly meets a woman shopping with her two sons, hinting at a repeat of the same dangerous pattern.
