François Merlin (Belmondo) is a Jean Bruce type writer of pulp espionage novels (he has written 42 so far) and about half of the film plays in his imagination, where he is the world-renowned superspy "Bob Sinclar" Christine is a sociology student who lives in Merlin's building and is interested in the novels, but in the writer's imagination she becomes Tatiana, his paramour, while the pompous and rich publisher of his novels, Pierre Charron, doubles as the great villain of the spy novels, the Albanian secret services head Karpov, who in a memorable scene of the film threatens to cut off one of Tatiana's breasts.
Writing his 43rd spy novel, François includes people from his life. He's the competent, sophisticated secret agent Bob in stark contrast to François. His cute neighbor is Tatiana who helps Bob in Acapulco.