Helen (Gwyneth Paltrow) is an insignificant office worker in a PR firm who looses her job for borrowing the office vodka. The movie follows two possible paths of her life based on whether or not she manages to catch a train on her way home from the office. In one version, she catches the train and meets James (John Hannah) with whom she feels an instant connection. Arriving home earlier she surprises her boyfriend Jerry (John Lynch), who lives with her, in bed with a mutual acquaintance, Lydia (Jeanne Tripplehorn). However, in the other version she misses the train, gets mugged and by the time she arrives home Lydia is gone, so Helen carries on her relationship as usual, only subliminally aware that something is not quite right. The film shows how Helen’s life differs, all due to a seemingly random chance.