Switch

Sophie discovers the Switch website through Claire Marras and agrees to swap her Montreal apartment for a Paris flat. She sees this as a chance for a carefree holiday, and begins making the exchange arrangements. The plan hinges on receiving the keys by mail and flying to Paris to take over the other woman's apartment.

Sophie flies to Paris and takes possession of Bénédicte Serteaux's apartment after the exchange is completed. She settles in with enthusiasm, awaiting a relaxed holiday in the city. The keys have been mailed, and she begins to imagine her time in Paris.

In the Paris flat, Sophie is delighted by the space but discovers a locked room she cannot access. She realizes she was not given the key, leaving a sense of unease alongside her excitement for sightseeing. Still, she enjoys her first day in Paris before the mystery deepens.

A brief encounter with a young man named Kourosh yields his phone number for a date later. The casual connection hints at normal life continuing despite the strange situation. Sophie feels a spark of normalcy amid the holiday setting.

The next morning, a police task force storms the Paris apartment and searches the premises. In the locked room, investigators find a headless corpse identified as Thomas Huygens, Benedicte Serteaux’s boyfriend. Sophie is arrested on the spot, with authorities assuming she is Benedicte.

At the police station, Sophie protests that she is not Benedicte, but evidence stacks against her. A passport in Benedicte Serteaux’s name with Sophie’s photo appears, and the internet footprint for Switch has vanished. The detective chief suspects a case of misidentified identity based on the missing links.

Sophie endures a harsh round of tests, including a rare-blood-type comparison that seems to confirm nothing. She suspects she was drugged, and in a tense moment at a dentist’s office she grabs a scalpel and forces an escape, risking further harm in the attempt to prove her identity.

On the run from the authorities, Sophie hijacks a car and uses the driver’s credit card to withdraw cash. She then hides in a small shop, buys clothing and a phone, and checks into a modest hotel for the night. The escape marks a turn from legal pursuit to a desperate flight.

Meanwhile in Montreal, a woman wearing a headscarf and sunglasses arrives on a Paris-bound flight and heads to Sophie’s address with a package. Detectives later question this woman, who claims to be Sophie Malaterre and challenges their assumptions about her identity. The threads of Paris and Montreal begin to intertwine.

Detective Forgeat interviews Alice Serteaux, Benedicte’s mother, and learns about their strained relationship. Forgeat secretly collects hair from Alice’s brush to pursue a DNA match, foreshadowing a key link between the families. The investigation expands beyond immediate appearances.

Sophie asks her mother Marianne to come to her Montreal address to search for proof of identity. Marianne eventually arrives and, guided by a phone update, enters the house with force, finding a gruesome scene: Thomas Huygens’s severed head on the bed surrounded by blood and candles. A masked woman attacks Marianne and sets the house on fire.

A hotel manager recognizes Sophie from TV news and calls the police. Forgeat, a fellow officer, closes in as Sophie proves to be a fast runner, eluding capture through gardens and streets with a motorbike dash toward a busy road. The chase stretches across Paris.

Back at the Paris police headquarters, a DNA analysis reveals that the headless corpse is Thomas Huygens and that Sophie and Thomas are half-siblings. The revelation traces back to their parents’ insemination histories, exposing a dark family secret that ties the cases together.

Sophie confronts Benedicte at her laboratory, where Benedicte confesses a brutal history and is about to kill Sophie. Forgeat and his team arrive, shooting Benedicte dead and freeing Sophie. In the aftermath, Forgeat comforts Sophie and confirms that she is finally safe.