Mark Renton, who has been living abroad for 20 years, returns to Scotland and reconnects with his old friends Sick Boy, Spud, and Begbie. As they navigate their complicated relationships and confront their troubled pasts, they become involved in blackmail, drugs, and criminal activities. Ultimately, they must confront their own demons and make choices that will determine their futures.

Renton, a heroin addict in Edinburgh, attempts to break free from the drug scene and his group of friends. He goes through withdrawal, relapses, and faces the consequences of his actions. Eventually, he leaves his friends and begins a new life in London. However, his past catches up to him when his friends, Begbie and Sick Boy, show up at his doorstep. Renton decides to leave them and takes a large sum of money from an illegal drug deal. He starts a new life, leaving behind the chaos and danger of his past.