Willard Stiles, a socially awkward and reclusive young man, lives in a dilapidated mansion with his overbearing mother. He works at a faceless company where he endures constant humiliation from his tyrannical boss, Frank Martin. Isolated and emotionally battered, Willard finds an unlikely solace in the company of a group of rats he discovers in the basement of his home, especially one intelligent and loyal rat named Socrates. Through daily interactions, Willard develops a deep bond with the rodents, training them to respond to his commands and finding companionship in their presence.

As his relationship with the rats grows, so does Willard's resentment towards those who mistreat him. He trains the growing army of rats to do his bidding, using them to take revenge on those he feels have wronged him. The newfound power emboldens Willard and gives him a sense of control he never had before. At the peak of his confidence, however, events begin to spiral unpredictably, as the boundary between his connection with the rats and his grip on reality start to blur. As things progress, the situation with the rats moves beyond Willard's control, escalating toward an inevitable and chaotic climax.