William "Bill" Boss (Dieter Laser), a notorious and sadistic prison warden in New Mexico, starts his day by watching The Human Centipede 2 (Full Sequence) alongside his accountant, Dwight Butler (Laurence R. Harvey). Despite the films garnering some enjoyment for Dwight, Bill openly expresses his disdain while being massaged by his assistant, Daisy ([Bree Olson]). In a grotesque display of power, he degrades Daisy by making inappropriate advances, insisting that women should stay silent on their opinions.
Their twisted routine is interrupted when they are called to handle a disturbing incident involving an inmate assault. Following the stabbing of an officer, Bill retaliates with merciless brutality by stomping on the arm of the offending prisoner, Tommy 'Tiny' Lister, inflicting excruciating pain and warning him of further punishment to come.
As they return to the warden’s office, Bill receives a bizarre delivery: a jar filled with dried African clitorises which he nonchalantly consumes for "strength." This unsettling moment escalates when he receives a prank call from an inmate, leading to a horrifying scene where Bill waterboards him with boiling water, resulting in irreversible damage. The inmate ominously declares that Bill has lost his soul.
In a sudden turn of events, Governor Hughes (Eric Roberts) arrives and demands an end to the escalating violence, threatening both Bill and Dwight with termination if they fail. In retaliation, Bill spirals deeper into madness, ordering a brutal "mass castration" of the inmates and gleefully indulging in the gruesome act himself. He even consumes the cooked testicles, branding them as "Energy Food." The atmosphere grows more sinister as Daisy is compelled to perform sexual acts for Bill while Dwight watches, only to later mistake the dried clitorises for candy.
Despite Bill’s initial dismissal of Dwight's peculiar suggestion of creating a human centipede by surgically joining inmates together, he becomes increasingly desperate for a method to establish dominance after a nightmare hints at his vulnerabilities. The arrival of the director, Tom Six, grants permission for Dwight's macabre vision, provided he witnesses the procedure himself.
The prisoners are shown the first two films in a menacing attempt to instill fear, which incites a riot, leading to chaos and injury among the guards. Bill and Dwight flee to safety, but the prisoners break in, resulting in horrific scenes of violence against Daisy. In an attempt to regain control, Bill employs tranquilizers on the prisoners, preparing them for the grotesque operation.
However, some inmates prove incompatible with the centipede plan, prompting Bill to eliminate them brutally. The duo learns of an inmate suffering from Crohn's disease, leading Bill to exact punishment by forcing him to be linked with his castrator in a repulsive twist of fate. In a repugnant act, Bill rapes the comatose Daisy, disregarding Dwight’s protests of love for her.
The operation gruesomely unfolds in front of Tom Six, who is horrified by the lengths taken to realize the centipede. To everyone’s shock, the 'Human Caterpillar' is also conceived, resulting in a grotesque installation of inmates stripped of their limbs. The shocking revelation that Daisy has been inadvertently included in the centipede shocks even Governor Hughes, who deems the entire endeavor insane and demands penalties for Bill and Dwight.
Yet, in a sudden twist, Hughes returns with a change of heart, voicing that this grotesque punishment is precisely what America needs. As the film concludes, Bill and Dwight toast to their perverse success, only for Bill to betray Dwight in cold blood for attempting to claim credit for the nefarious idea.
