Willard Stiles, portrayed by Bruce Davison, is a kind-hearted yet profoundly isolated young man struggling to connect with those around him, particularly his elderly mother, Henrietta Stiles, who is played by the iconic Elsa Lanchester. They reside together in a dilapidated mansion that echoes with their respective loneliness. The strained dynamic with his mother, celebrating his birthday with an atmosphere thick with well-meaning but suffocating advice, marks just one example of Willard's turbulent life. Among the guests, Charlotte Stassen, a character brought to life by Jody Gilbert, and Henrietta’s friends nag Willard relentlessly about embracing a more assertive personality and pursuing an executive position— a goal his mother doubts he's capable of achieving.
At work, Willard endures frequent belittlement from his boss, Mr. Al Martin, a figure embodied by Ernest Borgnine. The memories of Martin stealing Willard's father's company loom over him like a dark cloud. In the midst of this, he finds a modest refuge in the sympathetic nature of his co-worker, Joan Simms, whose slightly older perspective offers him some companionship. However, Willard's reality is often marred by a nagging sense of inadequacy, particularly when his mother insists that he deal with the rat problem in their backyard.
In a twist of fate, while attempting to deal with the pesky rodents, Willard discovers an unusual affinity for them. He saves a nest of rats and, through nurturing and playing with them, begins to realize he can train these creatures to follow him, effectively forging a new bond. He innovatively uses a well and a wooden bridge to manipulate their instincts, thus forming an unspoken allegiance. This newfound connection takes a darker turn when his mother falls ill, and Willard becomes increasingly entwined in the mentality of these rats, particularly with his clever pet, whom he names Socrates, and the rebellious Ben, who refuses to conform to Willard’s commands.
In the wake of Henrietta's passing, which leaves Willard to grapple with a heavily mortgaged home, he turns to his rats as accomplices in a series of petty thefts. The climax of his descent occurs during a chaotic dinner party hosted by Martin, where Willard's rats disrupt the proceedings, symbolizing the eruption of his suppressed rage. As the stakes rise, the combination of desperation and newfound control leads Willard to put his rats to use in an illegal scheme, burglarizing a wealthy client, Walter T. Spencer, who becomes a pawn in Willard’s drastic plans. As Willard's actions grow more audacious, we see the balance of power shift dramatically.
However, the encounter with Mr. Martin becomes a treacherous board for both Willard and the rats. In a violent confrontation propelled by vengeance, Willard unleashes his trained pack against Martin after a series of provocations culminate in tragic consequences. Willard's actions here evoke a powerful sense of betrayal, as he grapples with his morality and the dark path he is forging. As Martin meets his inevitable end—not simply by Willard’s hand but rather by that of their shared nemeses—the tumult of the previous events crashes down upon Willard, leading to his remorseful reflections and a poignant farewell to Ben.
The finale showcases the ultimate breakdown of Willard’s psychological and moral barriers. As he attempts to forge a new beginning with Joan, a relationship blossoming amidst debris from their tumultuous past, he is haunted by the aftermath of his actions. In a chilling climax, the once-loyal Ben becomes an adversary. Willard's desperate measures to rid himself of the rats spiral into a frenzy, ultimately leading to an escalating confrontation that ends with tragic finality. The film means to leave the audience questioning the vehicle of his transformation—both tormented and liberating—through the friendship and chaos spurred by the very creatures he sought to control. In this harrowing saga of loneliness, companionship, and the will to dominate, Willard's journey resonates with haunting familiarity amidst his poignant struggle with the dark companionship he unintentionally cultivated.
