Heroin addict Mark Renton stumbles through bad ideas and sobriety attempts with his unreliable friends --Sick Boy, Begbie, Spud and Tommy. He also has an underage girlfriend, Diane, along for the ride. After cleaning up and moving from Edinburgh to London, Mark finds he can't escape the life he left behind as Begbie and Sick Boy come knocking.

When a struggling comedian shows one act of kindness to a vulnerable woman, it sparks a suffocating obsession which threatens to wreck both their lives.