A lieutenant, at the head of a commando ready to land in France, finds among his men a maquisard who had tried to kill him in the past.

To conceal his nighttime infidelity from his wife Gisele, Pierre calls in a particularly shady private detective to concoct an alibi. He is introduced to a certain Robert Crémieux, who will pass himself off to Gisèle as a childhood friend with whom he spent the night until the early hours of the morning. The so-called childhood friend turns out to be a delinquent accused of burglary and rape on the very night he was supposed to be with Pierre. Pierre is immediately suspected of being his accomplice and, trapped by his own turpitude, arrested. Entangled in his lies and denials, he has to admit his infidelity to get out of the impasse.