Twenty years after betraying his friends and stealing their drug money in Edinburgh, Mark Renton returns home following the sudden death of his mother and the collapse of his life in Amsterdam. He reunites with his estranged acquaintances, each nursing lingering resentments. Sick Boy, now Simon, runs a failing, rat-infested Edinburgh pub and operates as a small-time blackmailer alongside his exasperated Bulgarian girlfriend, Veronika. Spud, still hopelessly trapped in heroin addiction and grieving the alienation of his family, attempts suicide before Mark unexpectedly saves him, reigniting their broken bond. Meanwhile, the volatile and psychotic Francis Begoo escapes from prison, consumed by a decades-old bloodlust and a singular desire to hunt down Mark and exact bloody revenge.Mark and Simon reluctantly decide to team up, securing a bank loan under fraudulent pretenses to renovate Simon's pub into an exclusive brothel. However, their fragile partnership is constantly threatened by mutual distrust and their chaotic past. Mark tries to make amends with Spud by encouraging him to channel his life experiences into writing, which slowly helps Spud find a renewed sense of purpose and self-worth. As the brothel plan progresses, Veronika begins acting as a financial catalyst, but she also grows romantically entangled with both Mark and Simon, creating intense friction. Complications multiply when Simon uses blackmail photographs of a corrupt local councilman to secure their business permits, drawing dangerous attention.Begbie eventually tracks Mark down, leading to a series of tense, violent encounters. After discovering his son has no interest in a life of crime, Begbie brutally forces his terrified offspring to participate in a series of armed robberies to fund his escape plan. The converging storylines collide when Begbie storms the newly opened brothel, violently confronting Mark and Simon in a desperate bid for retribution. During the chaotic confrontation, Spud arrives just in time to intervene, utilizing his unexpected cunning to help subdue the frenzied Begbie and lock him inside a trunk, effectively trapping his tormentor for the police.In the aftermath, the bruised survivors attempt to pick up the pieces. Simon and Veronika find a new, albeit unconventional, domestic equilibrium, while Spud finally reconnects with his
estranged wife and son, sharing his newly published manuscript about their shared history. Mark, having achieved a fragile
reconciliation with his past demons, revisits his childhood bedroom. Standing alone, he dances in place to Iggy Pop’s "Lust for Life," embracing the bittersweet nostalgia of his youth and finding a measure of hard-earned peace with who he has become.