The Lost

In the small town of Mauveton, 16-year-old Piper Willis and her best friend Hazel sit in a local café discussing a disturbing pattern: 11 teenagers have disappeared from the area in recent months, and police have classified every case as a runaway. Piper suspects something more sinister. Hazel proposes they spend the summer investigating by socializing at places where local teens gather, starting with the lake.

That same day, two wealthy college-aged men, Caleb and Owen, enter the café, and Piper notices Caleb looking at her. Later, on her way to the lake, Caleb approaches Piper and introduces himself. He expresses interest in her but acknowledges the age gap: She is 16, and he is 21. At the lake party, Hazel confronts friends of Lucie Bean, the most recently missing girl, but learns nothing useful. As Piper and Hazel leave, Caleb and Owen offer them a ride. Both girls accept. Once they are in the back seat, Caleb locks the doors and drives toward his family's private property without asking where they live.

Caleb takes them to a renovated building deep in the woods, surrounded by cornfields. Inside is a large recreational room with sofas, a TV, and games. He instructs Piper and Hazel to leave their phones on a side table, then leads them through a door with a keypad lock into a corridor lined with doors. Without warning, Caleb and Owen slip back through the door and lock it. Over an intercom, Caleb's voice instructs them to proceed to the end of the hall for "orientation." Terrified but seeing no alternative, Piper and Hazel push forward. In a darkened room, a video shows Caleb, Owen, and a third unidentified man welcoming them to "the game." After collecting bags of gray sweats, they pass through a red door, in front of which lies a white lily, a flower Piper associates with death.

Beyond the final door, they find four captive teenagers: Lucie Bean, the girl from the news article; Theo, 17, held for about two months; Kevin, held for about a month; and Priya, held for three weeks. Theo explains the building's purpose. Six numbered rooms line a corridor: rooms one through five subject captives to different forms of torture, including extreme sound, temperature, blinding light, sleep deprivation, and waterboarding. Room zero forces two captives to fight each other to the death. Both Theo and Priya have killed other captives in room zero. The captors periodically kidnap new teenagers to replace those who die. Cameras and intercoms monitor the captives at all times, and any attempt to ambush the captors results in immediate placement in room zero. Piper, drawing on the resilience she developed after her sister Penny's death three years earlier, resolves not to give up.

When Caleb calls Hazel's name, Piper volunteers to go in her place. She is sent to room two, where she endures cycles of extreme heat and freezing cold that leave her disoriented and shaking. She returns to the common room determined not to show weakness.

Early one morning, Piper and Theo discover all the doors standing open, including the front door. They run outside, but Piper insists it is a trap. When Caleb emerges from the trees holding a sword and Owen appears with a gun, her suspicion is confirmed. They rush back inside. While outside, Piper notices a window on the building's exterior wall near the waiting room, filing the detail away for later.

Over the following days, Piper endures room one, where piercing sounds leave her with a severe migraine, and room five, where Caleb waterboards her alongside Lucie. During a trip through the hallway, Piper discovers the waiting room wall is hollow plasterboard, likely concealing the window she spotted from outside. She shares this with the group, and they plan to break through on the day of a local charity fund-raiser when all three captors would be away.

The plan collapses when Lucie, traumatized by waterboarding, wakes from a nightmare and attacks the plasterboard wall, leaving visible damage. The captors take Lucie away for two days of sleep deprivation and reinforce the wall. Meanwhile, Kevin disappears, his fate unknown.

Shortly after, a new captive stumbles through the door: Evan, 19, who claims he was kidnapped six months earlier and held in solitary confinement after a failed escape attempt. He has been in room zero four times. Piper welcomes him, and they form a close bond. Evan reveals that the captors cannot hear audio through the intercoms, only see through the cameras, meaning the captives can speak freely.

Conditions worsen. The captors torment the group in the common room itself, blasting music, cutting lights, and raising the bedroom temperature overnight. Piper and Evan are called together to room three, where they endure blinding light; Evan shields Piper and coaches her through it. One evening, the captives' food is drugged. Piper and Evan wake tied to chairs, where Caleb and Owen beat Evan for hours while Piper is forced to watch.

Piper devises a final plan: set the building on fire using aluminum foil in the microwave. She reasons that smoke will draw the fire department, forcing the captors to open the doors rather than risk investigators finding bodies. The group agrees. Evan starts the fire, flames consume the room, and the door clicks unlocked. They sprint outside.

A gunshot stops them. Caleb stands by the door with a gun, flanked by Owen and Matt, the third man from the orientation video. Then Evan lets go of Piper's hand and walks toward the three men. In a devastating reveal, Evan explains that he is the true mastermind behind the entire operation. He created the building and its systems and entered the common room because he saw Piper and believed she shared his capacity for violence. Owen confirms that Evan "gets bored easily" and wanted to experience what he had built from the inside. When Evan signals Caleb, Caleb shoots Theo and Lucie dead. Matt objects, so Evan seizes the gun and shoots Matt, then shoots Owen when Owen hesitates.

Piper, Hazel, and Priya flee into the woods, where they discover grave sites and Kevin's mutilated body, confirming that Evan killed him. Caleb catches up, and Evan tackles Piper. As the two men argue, Piper snatches the gun from Caleb's hand, fires a warning shot, and orders them toward the emergency vehicles now visible by the burning building. Police arrive and arrest Evan and Caleb. Hazel and Priya reach safety.

At the police station, Piper reunites with her parents and gives a lengthy interview. She goes home and retreats to her bedroom. The narrative then shifts to Evan's perspective. In the police car en route to jail, Evan and Caleb strangle the two transporting officers with their handcuff chains, causing the car to crash. They steal a vehicle and drive back to town. Evan climbs through Piper's open bedroom window and covers her mouth. He tells her he loves her, insists they are the same, and threatens to kill her parents if she does not come with him. Piper packs a bag and leaves. Evan declares they will rebuild something bigger and better, calling them "one killer team."