The Girl on the Train is the story of Rachel Watson’s life post-divorce. Every day, she takes the train in to work in London, and every day the train passes by her old house. The house she lived in with her husband, who still lives there, with his new wife and child. As she attempts to not focus on her pain, she starts watching a couple a few houses down. She creates a wonderful dream life for them in her head, about how they are a perfect happy family. And then one day, as the train passes, she sees something shocking, filling her with rage.