Helen (Gwyneth Paltrow) is a public relations executive whose life is starting to fall apart on one fateful day. She just lost her job, and, on her way back home, she narrowly misses catching her train in the London underground...or does she.
At this point, the movie splits in two, alternating back and forth between two different worlds: one in which Helen caught the train, and the other in which she narrowly missed it. It's one minor difference, but the effects spiral away in completely different directions.
In the world where she catches the train, she arrives home in time to catch her boyfriend, Gerry (John Lynch), in the middle of an affair with another woman (Jeanne Tripplehorn). Yet, as traumatic as this seems at first, it makes her a stronger woman, as she pursues a new career, and a new life with a new love, James (John Hannah).
However, when she missed the train, her life turns out radically different. Gerry continues his affair with Lydia, unbeknownst to Helen, who, in the meantime, is forced to work multiple menial jobs to support the two of them.
Although the parallel storylines might seem somewhat confusing at first, especially to someone who is unprepared for the premise of the film, the filmmakers do an admirable job at reducing the inherent confusion. Each Helen is marked in an identifiable way (first with a bandage, and then later with differing hairstyles) so the confusion is kept to a happy minimum.
Once confusion is laid to rest, the biggest problem with running parallel storylines like this is that one of the storylines might easily overpower the other. This is somewhat the case here, but it never becomes an outright disaster. The "catches-the-train" Helen has the more vibrant of the two plots, and though the other Helen might get more pity, there's no question of which one we'd like to spend the time with. The trouble is each storyline gets roughly equal time, which means you spend half the movie waiting for the other half.
Paltrow manages the double role well, proving that her recent doldrum has been the result of poor material rather than a lack of talent. Of the two male leads, John Lynch actually comes out on top (even though he's playing the shadier of the two men). John Hannah just doesn't have that much to work with, playing a Mr. Right.
Sliding Doors deserves points for being original. However, an unfortunate side effect of its split perspective is repetition. One crucial plot point actually happens four separate times (nearly becoming an unintentional running gag). And (magical musical chimes aside) there's never an explanation for the parallel stories. Perhaps it's just a mental exercise for the audience...anyhow, an ending revelation nearly makes the whole thing pointless.
Still, the movie is enjoyable, and what more do you want from a romantic comedy?