This is a very unusual film. Sliding Doors explores the differences a life would take if a small yet trivial event changed. The event is catching a subway train. In one reality, Helen Quilley catches the train, and catches her boyfriend in bed with another woman. In another reality, she misses the train, and thus does not catch her boyfriend in bed with the other woman. Throughout the film, we see the parallel realities play out. In neither reality is Helen happy all the time, nor miserable all the time. Life is not so one-dimensional.

Sliding Doors is built around characters who act fairly like real people. You really believe in these people because they are fully fleshed out in both realities. What makes this film work is the direction and editing. Transitions between realities are smooth, yet there is never any ambiguity about which reality we are looking at, even when that reality changes in mid-shot.