When Helen, a London ad executive, is fired from her job and rushes out to catch a train, two scenarios take place. In one, she gets on the train and comes home to find her boyfriend, Gerry, in bed with another woman. In the second, she misses the train and arrives after the woman has left. In the first scenario, Helen dumps Gerry, finds a new man and gradually improves her life. In the second, she becomes suspicious of Gerry's fidelity and grows miserable.