The film portrays the life of Michael Peterson, a man who renames himself Charles Bronson after the famous actor. Bronson begins his story in a quiet English town, growing up with aspirations of fame. However, his penchant for fighting quickly lands him in prison for a botched post office robbery for which he is sentenced to seven years. Prison, however, becomes a stage for Bronson’s violent acts and eccentric behavior, and he continually seeks out trouble, relishing the notoriety it brings. His violent outbursts and confrontations with guards quickly extend his sentence, and he spends the majority of his time in solitary confinement, forging his reputation as Britain's most violent prisoner.

Bronson's tale is told through a series of dynamic and often theatrical vignettes, illustrating his descent into infamy. Outside brief periods of release where he tries his hand at bare-knuckle boxing, he consistently finds himself back behind bars. Yet despite such confinement, he embraces his persona, treating his life as an ongoing performance, and expresses himself through art and surreal storytelling. Early on, we see him wrestle with the identity he has crafted, whether through fights, or flamboyant theatrical displays, but his relentless aggression and knack for chaos perpetuate his cycle of imprisonment. The journey underscores his struggle for self-expression and the contradictions within his violent search for fame and identity.