The film opens with a young man who has fled from home, portraying a meek and unassuming geek with thick glasses. He shares his bus journey with another runaway named Matt Soulby, who has escaped from military school. Their adventure takes a turn when the bus suffers a flat tire, pushing them to purchase a second-hand car from a local mechanic. Unfortunately, they encounter another flat tire, and during the repair, Matt is tragically pushed into the path of an incoming vehicle, resulting in the deaths of both him and the car's driver.
In a gripping narrative, Angelina Jolie stars as Special Agent Illeana Scott, an FBI profiler dispatched to Montreal to assist in unraveling a murder case. Her unconventional profiling methods become apparent as she visits crime scenes, even lying in the position of the victims to glean insights that escape the police's attention. Delving deep into the mind of the elusive serial killer, she theorizes that the murderer is assuming the identities of his victims.
The plot thickens as the mother of the serial killer, Mrs. Archer (played by Gena Rowlands), unexpectedly spots her son—who was presumed dead—on a ferry. She seeks the police's help, pursuing Paquette, but her pleas fall on deaf ears, with the case remaining closed. However, as the body count rises, an artist named James Costa (Ethan Hawke) becomes the key witness, able to sketch the killer’s face, yet unable to recall essential details.
With the investigation in full swing, Agent Scott perseveres, convinced that the murderer is the non-favored younger twin in a set of twins. Despite police protection for Mrs. Asher, she declines to register her home, prompting Illeana to explore the place herself. In a rundown penthouse filled with disturbing relics of childhood, she faces a shocking encounter with an unknown assailant who vanishes into the shadows.
As the tension mounts, Agent Scott finds herself entangled in a romantic relationship with Costa, which clouds her judgment and makes her reconsider her involvement in the case. Yet the Canadian authorities believe she remains their best asset and refuse to let her off the case. Dubbed as bait, Costa encounters perilous situations as he navigates through the plot’s intricacies.
The suspense culminates in a confrontation between Costa and his malevolent twin, Hart, leading to a violent clash where Costa is injured, while Hart's escape ends tragically when his car explodes. Costa survives, and the aftermath sees him and Illeana in an intimate moment.
The emotional stakes rise when Mrs. Asher confronts the reality of her son’s demise, choosing silence in a moment of shock as she gazes into his lifeless eyes. Unfortunately, the police mock her loss. Illeana's instincts draw her to follow Mrs. Asher, who has taken a chilling elevator ride with Costa—the twin she never wanted to face. The grim discovery of Mrs. Asher's bloody fate raises alarms.
As the timeline progresses, the narrative shifts, and Illeana finds herself back in the U.S., stripped of her badge and living in dire circumstances, unexpectedly pregnant. A confrontation looms when Costa reappears, his demeanor altered, marking a significant threat to her and her unborn children.
Their final showdown leads to a harrowing struggle where Illeana must utilize her wits and resolve. In a heart-pounding climax, she cleverly reveals her deception about the pregnancy just as she fights for her life, driving a pair of scissors deep into Costa’s heart. In his final moments, she confronts him with the truth of her ruse, ensuring that his reign of terror is finally over.
With the dust settling, Illeana reaches out to Leclair, who expresses relief at hearing from her, agreeing to help her face the impending inquiries and paperwork, closing this harrowing chapter of violence and deception.
