Content Warning: This guide discusses situations of violence, murder, antigay bias, fat phobia, sexism, and xenophobia that appear within the novel.

Private detective Sam Spade is in his office when his secretary, Effie Perine, informs him that a potential client is waiting to see him. The client is a timid, soft-spoken, attractive young woman named Miss Wonderly. Initially, she is unsure of where to start, but Spade’s calm confidence puts her at ease, and she explains her situation from the beginning. She is from New York and in San Francisco because her 17-year-old sister, Corinne, has run away from home with an older man named Floyd Thursby. Their parents will be home from Europe in two weeks, and she wants to bring Corinne home before they arrive. After failing to contact her sister, she has arranged a meeting with Thursby at her hotel that night. While she is reluctant to outright say it, it is implied that Corrine is pregnant and that it is impossible to cover it up, because Thursby is already married and has a family in England. Spade and his partner, Miles Archer, agree to help Wonderly and devise a plan to tail Thursby and find Corrine after their meeting that night.