The third in a series of films featuring François Truffaut's alter-ego, Antoine Doinel (Jean-Pierre Léaud), the story resumes with Antoine being discharged from military service. His sweetheart Christine's (Claude Jade) 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 (Delphine Seyrig), and finds that he must choose between the older woman and Christine.