In Sliding Doors, Helen is a successful publicist in London who is fired from her job on the same day she discovers her boyfriend Gerry is cheating on her. As she rushes to catch a train home, the movie splits into two parallel storylines - one where she catches the train, and one where she misses it.
In the first storyline, Helen catches the train and arrives home to find Gerry with another woman. She eventually moves on from him and starts a relationship with James, a kind-hearted man whom she had previously met on the train. Meanwhile, in the second storyline, Helen misses the train and is mugged while waiting for the next one. As a result, she cuts her hair short and dyes it blonde, taking on a more confident and assertive personality. She eventually meets James as well, but their relationship is complicated by her ongoing affair with Gerry.
As the two storylines unfold, they intertwine in surprising ways - Helen's decisions in one storyline affecting events in the other. For example, in the second storyline, Helen's increased confidence leads her to confront her cheating boyfriend and demand the truth. This prompts Gerry to break things off and move out, freeing her up to pursue a relationship with James. Meanwhile, in the first storyline, Helen's trust in Gerry is shattered when she discovers he lied to her about attending counseling, causing a rift in her relationship with James.
Overall, Sliding Doors is a charming and clever romantic comedy that explores themes of fate, love, and the choices that shape our lives. With its witty script, strong performances, and inventive structure, it has become a classic of the genre.