The story is a first-person narrative told from the point of view of three women: Rachel, Anna and Megan. Rachel Watson is a 32-year-old alcoholic reeling from the dissolution of her marriage to Tom, who left her for another woman. Rachel's drinking has caused her to lose her job and have frequent binges and blackouts, during which she harasses Tom by phone and sometimes even in person. He is now married to, and has a daughter with, his former mistress Anna – a situation that fuels Rachel's self-destructive tendencies, as it was her inability to conceive a child that sparked her alcoholism. Concealing her unemployment from her flatmate, Rachel follows her old routine of taking the train to London every day, looking longingly at her former house (occupied by Tom and his new family) and usually drinking on the return home. She also begins compulsively watching an attractive couple who lives a few houses away from Tom, fantasizing about their perfect life together. Rachel has never met them and has no idea that the woman, Megan Hipwell, is actually unhappy in her marriage and helps Anna care for her child. Struggling with her troubled past, Megan starts seeing a therapist, Kamal Abdic, to whom she is attracted.