Heroin addict Mark Renton (Ewan McGregor) stumbles through bad ideas and sobriety attempts with his unreliable friends – Sick Boy (Jonny Lee Miller), Begbie (Robert Carlyle), Spud (Ewen Bremner) and Tommy (Kevin McKidd). He also has an underage girlfriend, Diane (Kelly Macdonald), along for the ride. After cleaning up and moving from Edinburgh to London, Mark finds he can't escape the life he left behind when Begbie shows up at his front door on the lam, and a scheming Sick Boy follows.