Set 225 years after a nuclear holocaust in 2015, the world is split between the comfortable underground cities and the daylight-drenched “New Primitives.” A small group of 11 survivors, including Chocolate [Geretta Geretta], Kurt [Ottaviano Dell'Acqua], Video [Gianni Franco], Lucifer [Jean-Christophe Brétignière], Taurus [Massimo Vanni], Deus [Fausto Lombardi], Diana [Cindy Leadbetter], Myrna [Ann-Gisel Glass], Duke [Henry Luciani], Lilith [Moune Duvivier], and Noah [Christian Fremont], stumbles upon a mysterious, abandoned village while exploring the surface.
Inside, they find plenty of food, a greenhouse with fruit trees, and a reservoir of drinking water, and they decide to settle in despite the memory of numerous horribly mutilated corpses scattered around the town. Their cautious hope is short-lived, however, as a nightmare begins to unfold after nightfall: hundreds and hundreds of hungry, genetically mutated rats swarm the area, picking off the unprepared one by one.
Tension rises quickly as personal loyalties come under strain. Lucifer and Lilith are discovered making love, and their activity angers the others, who expel them for their loudness. After a heated argument, Lucifer becomes intoxicated and is dragged into a sewer where he is consumed. Almost simultaneously, Lilith is attacked and eaten from within; a rat later claws its way out from her mouth, a grisly sign that the danger is closer than anyone imagined. Noah also falls prey to the onslaught, and Kurt, the group's apparent leader, is forced to shoot him with a flamethrower to end his suffering.
With dawn still a distant hope, the survivors barricade themselves in the village basement and wait. Diana is bitten and begins to deteriorate, leaving Chocolate to tend to her wounds and warn that infected bites must be treated promptly or they will spread. The men venture out to gather medicine and water, while the women keep watch. Duke refuses to help, retreating to a safe corner instead of lending a hand.
Tragedy compounds as Taurus is pulled into the stairwell and devoured during a chaotic escape attempt. The strain fractures the group’s fragile authority: Duke’s mind buckles, and he challenges Kurt for control, ultimately kidnapping Myrna in a reckless bid for freedom. Their escape attempt ends in tragedy when Duke drops a grenade, killing himself and Myrna in the process. Grief and fear push Diana to desperate measures, and she takes her own life, slashing her wrists; her partially eaten body is later found by the survivors.
They uncover a distressing recording from a man who warns that the town’s fate will mirror his friends’ if anyone ventures inside. Still under siege, the remaining four survivors face another brutal assault from the rats. In a final act of sacrifice, Deus and Kurt barricade the door to allow Video and Chocolate to slip outside. A rescue team in hazmat suits arrives from the underground Delta-2 sector, gun and gas masks in place, and they slaughter the rat swarm to save the two.
Gratitude is tempered by awe as the survivors realize their rescuers are not merely other humans but fellow underground dwellers who share their humanity. As they thank their saviors and speak of their common race, the leader of Delta-2 pulls off his mask, revealing himself to be a humanoid rat, a shock that reframes the entire encounter and casts the struggle for survival in a startling, unsettling new light.
