For a true trainspotter, a diesel locomotive is what drugs are to Mark Renton. Mark pursues his hobby with passionate dedication. He doesn't miss a train, a drink, or a hit. Renton has hit rock bottom, and he is mostly high.

The fellow travelers on Renton's journey are Spud, a sweet simpleton who is addicted to dope; Sick Boy, whose true addiction actually revolves around James Bond films; and Tommy, who rejects drugs and is addicted to the great outdoors. Then there's Begbie, a ticking time bomb on the way to hell. Begbie's fuel is alcohol, and his favorite drug is a good fight.

But Mark's train has not yet left the station. At some point, he thinks, he will manage to get by without the substance. Maybe.