Rachel Watson has, to put it mildly, seen better days.
An unstable alcoholic who is prone to blackouts, she no longer has a husband, job, or home. Instead, she’s reduced to living with a friend and spending her days riding the train because she has nothing better to do with her time. She distracts herself by watching a couple who live in a house next to the railway track.
As she rides by every day, she crafts a story in her head about this seemingly perfect couple. She gives them names and occupations and hobbies. And, yes, that’s as creepy as it sounds. This unhinged respite from her own troubled life is shaken one day when she rides by and sees something that shatters the illusions she has created in her own imagination.
Even more worryingly, she learns soon that the woman who lives in the house has disappeared. Rachel starts to suspect that she may know more about the case than she realizes, but she can’t remember anything. Complications ensue.