Sardonic Parisian police inspector Lechat (Serge Reggiani) and his jovial partner, Chemin (Philippe Léotard), are assigned to investigate the mysterious death of the wealthy Monsieur Richard (Jean-Pierre Aumont). It's difficult to tell whether the successful businessman committed suicide or was murdered. The dead man's beautiful wife (Michèle Morgan), who had just discovered her husband's infidelity, is suspected, as is a terrorist group that had been threatening him prior to his death.