I found this movie a few years ago. I loved it! It took the question of "what if...?" and followed the premise of how the character's life changed and strangely stayed the same. In the movie, Helen is living with her boyfriend of 2 1/2 years, a writer named Gerry. The week-end after her birthday she wakes up late and goes to work like normal and gets fired. Then she's heading home again and misses the train.
At this point, the movie does a rewind to her running and catching the train home. Now, we watch the two life paths of Helen unfold. In one view, Helen misses the train and has to catch a cab. And as she's waiting for the cab, someone comes up to mug her, or rather attempts to mug her. And on the other path where she has caught the train, Helen talks to an exuberant stranger (James Hammerton(picture is of Helen and James on the train)) she had run into earlier, gets home early and finds her boyfriend in bed with his ex-girlfriend.