A corrupt, junkie cop with bipolar disorder attempts to manipulate his way through a promotion in order to win back his wife and daughter while also fighting his own inner demons.

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 when Begbie shows up at his front door on the lam, and a scheming Sick Boy follows.

First there was an opportunity......then there was a betrayal. Twenty years have gone by. Much has changed but just as much remains the same. Mark Renton (Ewan McGregor) returns to the only place he can ever call home. They are waiting for him: Spud (Ewen Bremner), Sick Boy (Jonny Lee Miller), and Begbie (Robert Carlyle). Other old friends are waiting too: sorrow, loss, joy, vengeance, hatred, friendship, love, longing, fear, regret, diamorphine, self-destruction and mortal danger, they are all lined up to welcome him, ready to join the dance.