Callum [Toby Kebbell] arrives at a small juvenile facility run by Jed [Sean Pertwee], where a tight-knit but turbulent group—Steve [Stephen Wight], Blue [Adam Deacon], Jethro [Richie Campbell], Lindsay [Ben McKay], Davie [John Travers], and Lewis [Luke Neal]—exists under a tense mix of bravado and bullying. The crowd’s rough dynamic seems to peak when Davie and Lindsay are taunted, and Davie’s suicide by slashing his wrists becomes a chilling turning point. Davie’s dad learns of the tragedy, and the entire group, along with Jed, is sent away for a team-building exercise on a remote island. From the moment they land, something about the place feels off, as if the island itself is watching them with silent intent.
The mood shifts as Callum is knocked unconscious by an unseen force, and the rest of the group discovers him later, discovering the island’s eeriness while they swim. A campfire appears in the distance, and Lindsay is suddenly taken by a hidden menace. They encounter a small, organized group of women led by Louise [Alex Reid], with Jo [Karly Greene] and Mandy [Lenora Crichlow] among her charges. To keep tensions in check, Jed and Louise agree to keep the groups separate, though a spark of romance soon flickers between Jo and Lewis.
A desperate chase story unfurls when Steve and Lewis stumble upon a homeless man; the man defends himself with a stick, and Steve responds with brutal force, leaving the man dead. Callum discovers the grim scene, and when he fingers the blood on his hands, Jed finds him and cuffs him to a tree. The emergency phone goes missing, and Jed blames the group, incensing Steve. In response, Jed and Louise decide to merge the two groups for safety, tightening the knot of danger around everyone involved.
The following morning, Jethro wakes, seeks water, and is attacked. Jed orders Blue and Lindsay to investigate and they return with the grisly evidence of a dismembered arm in the water. An ambush follows: Jed is shot with arrows, disemboweled, and mauled by four dogs that appear to respond to a whistle. Louise and Callum try to flee as the dogs close in, but Louise sacrifices herself, leading the pack away and is dragged off a cliff.
The survivors stumble upon Jethro’s body, found hanging from a tree with the letter D carved into his flesh. They locate a cabin to hide in, where Lindsay reveals what he knows about the killer: Davie’s dad. The next morning, Blue makes a brutal, attempted sexual advance on Jo, provoking a furious response from Lewis. Blue is eventually killed when he steps into a bear trap, despite Mandy and Callum’s attempts to free him. Davie’s dad then uses smoke to drive the group from the cabin.
As fear spirals, Steve abandons Lindsay to struggle on alone. They later discover Louise is alive but badly injured, so the surviving trio places her in a dry, safe spot while they search for a boat. Louise is murdered in camouflage by Davie’s dad, who slips in unseen and slashes her throat. The group splits to search for rescue; Steve teams with Lewis, while Callum partners with the girls. Steve finds a boat but contemplates leaving the others behind, a plan that Lewis initially supports until it becomes clear the fuel line is cut. Davie’s dad fires a flaming arrow, setting the boat on fire, and the dogs are summoned again. Steve and Lewis scramble up a rock face to escape, while the others wade through the water.
In a brutal turn of events, Steve and Lewis corner Lindsay and use him as bait for the dogs. The pack is recalled, but one dog remains and Callum shoots it. They later discover Louise’s head mounted on a stick with Davie’s name scrawled in blood, prompting Callum to sever the dog’s head in retaliation. The survivors resort to cannibalism, cooking the dog to survive the night.
Callum ascends to the island’s highest point, lifting the dog’s head as a grim distraction for Davie’s dad. The next morning, Steve and Mandy collide over what to do next; Steve lunges at Mandy, but Lewis manages to subdue Steve while Mandy escapes. Jo warns Steve that he is poison and that Lewis no longer needs him, prompting Steve to kill Lewis. Jo screams for help, but Steve leaves her to her fate; she dies in a trap, burned alive after pleading for mercy.
Steve later corners Lindsay, ties him to a tree, and dares Davie’s dad to witness the boy’s supposed bullying as a form of revenge. Davie’s dad arrives, pressing Steve to reveal his pain and to cut his own wrists, a savage moment that ends when Steve is shot in the head by a crossbow. Davie’s dad frees Lindsay and orders him to meet by the boat, a plan Mandy overhears as she hides. Callum confronts Davie’s dad, and the two square off.
A brutal duel ensues: Callum wounds Davie’s dad with an axe and pursues him with a crossbow. Lindsay betrays everyone, admitting to Davie’s dad that he orchestrated the killings, and silently backs away toward the cliff—only to fall to his death. Callum’s bid to finish Davie’s dad by crossbow is foiled by fate, as the killer succumbs from his wounds on the beach. Mandy and Callum reunite, and Callum delivers a stark, haunting line: everyone died on the island. With the island behind them, they board a boat and depart, leaving the island’s grim footprint behind them.
> everyone died on the island
