After humanity wins a war against zombies, tourists are able to kill zombies for sport at the Rezort. Guests include couple Lewis and Melanie, who want to conquer Melanie's psychological issues caused by the zombie war; Archer, a quiet veteran; Jack and Alfie, teenage video gamers; and Sadie, whose ex-fiancé dumped her prior to their wedding. After the group meets the owner of the resort, Valerie Wilton, Archer sees Sadie sneak into a control room. There, she hacks into a mainframe, causing the system to become erratic. The engineers, scared they could lose their jobs due to careless system security, keep quiet about the problems as they attempt to fix the system.
After meeting their guide, Nevins, the guests leave the resort to hunt zombies. The first group of zombies are restrained in place and easily killed. The second group roam freely, and the guests snipe at them from a safe distance. Despite Lewis' urging, Melanie can not bring herself to shoot one. Archer surprises the others by scoring many rapid head shots, later explaining that he has come to the resort because killing zombies is the only thing he was ever good at. Nevins leads them to a safe spot, and they camp for the night. When they can not sleep, Melanie and Sadie discuss the ethics of killing zombies for sport, and Sadie says she believes it leads to a decreased inhibition to harm the living.
After several system failures, the resort's security system goes offline. Zombies are released from their fenced-in pens, killing the guests and staff in the resort. Wilton escapes to her office, sealing the door behind her and dooming the remaining engineers. The guests outside the resort in the safari do not realize what has happened until the now-freed zombies attack them. Alfie is killed in the melee. Nevins tells them the entire island will be firebombed in several hours as a failsafe, and their only hope is to escape to the docks. Nevins' SUV fails to start, and Archer leads them on foot toward the docks. As they pass through a security checkpoint, Nevins is bitten. Lewis angers Melanie when he kills Nevins with a head shot.
When the guests are on their way to the docks, Archer threatens to leave Sadie behind unless she reveals her involvement in the resort's problems. She admits to being a member of a zombie rights activist group and says she merely copied documents from the resort's mainframe to prove the resort's danger. Jack says she has been used to inject a virus in the system and cause the destruction of the resort. Although angry at her actions, Melanie promises Sadie she will not be left behind. After zombies attack, the guests get caught in tunnels and suddenly Archer, Melanie, and Lewis go one way, and Jack and Sadie another. Sadie is bitten and sacrifices herself to give Jack time to escape. Before she dies, she gives him her evidence.
Jack rejoins the others, and they enter the resort. After wandering through a security area, they discover the resort has been using a charitable front organization to lure refugees to the island, where they are transformed into zombies. Jack is bitten, and Archer kills him. As Archer and Melanie hold back zombies, Lewis abandons them. Archer tells Melanie to flee to the docks and apparently sacrifices himself. Near the control room, Melanie encounters Lewis, who has subsequently been bitten. Instead of killing him, she hands him her pistol which he uses to shoot himself in the head.