The third in a series of films (following The 400 Blows and the short Antoine and Collette) featuring writer-directed François Truffaut's alter-ego, Antoine Doinel (Leaud), the story resumes with Antoine being discharged from military service. His sweetheart Christine's father lands Antoine a job as a security guard, which he promptly loses. Stumbling into a position assisting a private detective, Antoine falls for his employers' seductive wife, Fabienne, and finds that he must choose between the older woman and Christine.