Society collapses under the weight of a virulent outbreak, with the infected turning into cannibalistic killers. When Evie’s husband John becomes separated from the group during a brutal attack, the survivors retreat to an emergency shelter. Gary and Evie want to hold their line and wait for John, as they had agreed they would do in such a crisis, but Bob grows increasingly impatient, insisting that realism demands a safer, more permanent shelter. Although Bob initially backs down, he later forcefully seizes the group’s car, rifle, and supplies. When Gary objects, Bob shoots him, leaving the group shaken and leaderless. Sammy, the group’s mechanic, and Marge, Bob’s wife, choose to leave with him, taking crucial gear and supplies, and they abandon Evie to fend for herself.
John eventually returns, furious to discover Evie and the others had left with most of the resources. Evie’s protests are cut short when Sammy trudges back, delirious and clearly infected. John shoots Sammy as she begins to transform, and the two survivors press on, trying to make it on their own. But the world outside is swarming with the undead, and a relentless siege closes in. Just as despair seems final, a stranger named Charlie intervenes and saves them, though John greets him with suspicion, noting they have nothing of value to steal. Charlie explains that what he seeks is companionship and an opportunity to share his supplies, and Evie, wary but hopeful, accepts him into their small trio.
As the new trio settles, it becomes clear that Charlie’s presence shifts the dynamic. John shares that he used to be a college professor and Evie a schoolteacher, while Charlie presents himself as a family man who has suffered a terrible loss. Charlie’s practical skills gradually improve their quality of life, yet Evie remains haunted by John’s earlier suicide attempt and questions whether Charlie’s motives are as purely benevolent as they seem. Charlie reassures her that he can provide more than John, and for a time, she is swayed, though her unease persists.
A crisis amplifies the tension: John endures a serious asthma attack, and Evie pleads with Charlie to find medicine. Charlie hints that he knows where it might be, but he will only fetch it if Evie agrees to a sexual favor. Desperate, she yields. Later, Evie discovers evidence that Charlie lied about having a family, a realization that doesn’t easily erase the fear that she is being drawn into a fragile web of dependence. John is initially skeptical but argues that they need Charlie to endure the harsh reality outside.
The fragile balance shatters when Charlie reveals a darker secret: he keeps a former lover—now infected—chained in his car to observe. Charlie returns in anger, declaring that survival is the only rule in this new society and that, given their dependence on him, he deserves whatever he desires. John surrenders his pistol to Charlie, and watches in horror as Charlie drags Evie into the shelter to assault her again. Evie’s cries haunt him, yet he remains paralyzed by fear and pain.
A lost soldier appears, and John disarms him, learning of an extraction point and the possibility of escape. In a final, brutal turn, John kills the soldier and shoots Charlie. As Charlie dies, he fires a shot that strikes Evie’s arm. John quickly patches her up, but she fights to stay conscious amid the chaos.
Charlie's car breaks down near the extraction corridor, and the looming horde of zombies converges on their location, drawn by John’s shouting. He urges them to move on foot, but Evie falters. After several pleas to stand, John finally hands her a pistol and, realizing he’s being left behind, Evie shoots him in the leg to create a distraction and slips away, using him as a decoy while she makes a break for the extraction point. The desperate chase ends with Evie reaching safety as John is overwhelmed and devoured by the advancing zombies.
