Paul Harris, a divorced high school teacher and basketball coach, finds his everyday world upended as a terrifying crisis unfolds around him. He finds himself drawn into the escalating nightmare alongside Dr. Louis Spenser, a professor and rat expert whose scientific insight helps them piece together what’s happening, and Kelly Leonard, the health department inspector who becomes a crucial ally in the city’s fight for survival. Together with Trudy White, a spirited high school cheerleader, and his students, Paul must navigate a city spiraling from an outlandish threat into a full-blown emergency.
Giant rats, the size of small dogs and fed on steroids, begin the crisis by losing their homes when Kelly orders the granaries burned. The rodents migrate from the mountains of grain into a suburban home where unsupervised teens provide easy prey, and the danger quickly escalates from ominous to deadly. The first grim toll comes when a toddler, left unattended in a high chair, becomes a victim, and the danger deepens as an elderly man, Henry Younger, is attacked on the snowy streets. The threat reaches a fever pitch when George Faskins, a health department field inspector, plunges into the sewers to confront the burgeoning swarm. In the damp bowels of the city, he confronts the rats, and the encounter ends with his untimely demise, marking a turning point in the city’s response to the crisis.
As Paul talks with Dr. Louis Spenser, the scientist concludes that the steroid-laced feed may have created a new, more aggressive breed of “super-rats” that have oozed into the sewers in search of food. In response, the Health Department initiates a citywide fumigation, a plan that proves disastrously ineffective. The death of the rat expert confirms the futility of the first strike, and the nightmare expands beyond the sewers to everyday life: the rats invade a bowling alley and a movie theater, turning a crowd into panicked prey. The massacre reaches a public spectacle when the rats attack viewers at a Bruce Lee film, causing chaos, sustaining casualties, and forcing people to flee in terror. In the midst of this chaos, the city witnesses the loss of Trudy White, among others, as the swarm demonstrates that no place is safe from the rampage.
Meanwhile, the city’s mayor, Rizetti, pushes ahead with his plans for a new subway inauguration, unaware that the rats have already set their sights on the underground routes. As the threat closes in, Rizetti and his delegation scramble to safety, with the mayor ending up aboard an empty subway train as chaos erupts above. Paul, driven to stop the spectacle, wrests a revolver from a frightened officer and descends into the tunnel. He, along with Kelly Leonard and his own son, Tim Harris, navigate a disabled subway train and the derailed risk that the rats pose to the passengers. The trio finds a temporary refuge in a fenced maintenance area that the rats use as a nest, where they improvisationally prepare for a desperate escape.
Armed with cutting torches and drums of flammable liquids, they improvise a daring plan to trap and destroy the swarm behind them. A fiery explosion erupts, wiping out the rats in their wake as the trio races back onto the subway car, hoping they have outrun the worst of the carnage. The platform outside glows with the aftermath, and a chilling final image returns: on the same train, the few survivors share a fraught moment of relief, only to glimpse a lingering horror—snared by the feast of a few remaining rats that gnaw at the mayor’s body, a grim reminder that danger can linger even as the city believes it has escaped. A final, unsettling sight—a bloodied rat hisses at the train window—caps the film with a stark, eerie note that there are some horrors that continue to stalk the city even after the lights go up.
