Edmond Murray, portrayed by James McAvoy, finds himself in a desperate situation when he is summoned to the scene of his son Ethan's mysterious disappearance. As he arrives, he encounters his ex-wife, Joan, played by Claire Foy, and offers her a moment of comfort amid the chaos. With no time to waste, Edmond quickly joins a search party and gets grilled by the police concerning his son's whereabouts.
Following the police interview, Edmond seeks out Joan's new partner, Frank, leading to an intense conversation. When Edmond learns of Frank’s plans for a new home that lacks proper accommodations for Ethan and discovers that Frank has been giving Joan Valium to help with her distress, he spirals into a rage. He confronts Frank in the kitchen, where a physical altercation ensues, resulting in Edmond knocking Frank out cold and subsequently calling Inspector Roy to investigate.
Though Edmond is arrested, no charges stick, as Frank chooses to overlook the incident, acknowledging Edmond's emotional breakdown. However, Inspector Roy later shows up to deliver unsettling news: Edmond has been removed from the investigation without any given explanation. In a moment of desperation, Edmond discovers Frank's phone and finds damning videos depicting Ethan in the lead-up to his disappearance. He notices a car appearing in both videos, barely visible but crucially present.
With the help of Joan’s brother, who has connections in the insurance field, Edmond tracks down the vehicle's owner and pays the location a visit. As he lies in wait, he ambushes an individual arriving in the car, wielding a crowbar to subdue him. This stranger, under duress from an aggressive interrogation involving a blowtorch, admits to facilitating the kidnapping of children by sending their photos to interested parties.
Time is of the essence, and Edmond learns where his son is being held, prompting a frantic rush to a nearby lodge. With a determined will, Edmond disables the captors' vehicle and confronts one of their henchmen, successfully rescuing Ethan and informing Joan and Inspector Roy of their location. However, their escape is cut short when Edmond is shot, leading to a dangerous crash.
In a heartfelt moment by the water and mountains, Joan and Ethan hide behind a tree while Inspector Roy brings them to safety. As the sun sets on this harrowing ordeal, Joan, Edmond, and Ethan share a serene moment watching Ethan fly his remote-controlled quadcopter. With law enforcement breathing down their necks, Roy advises Edmond to make his exit, as he prepares to say a teary goodbye to his son. As the credits roll, Roy hints that Edmond's crucial actions may play a pivotal role in any future court decisions regarding the extensive kidnapper network that is soon to be taken down.
