Fictionalized reconstruction of the life of the French spy Marthe Richard who decided to contact the secret services during the First World War.

Pépé le Moko, one of France's most wanted criminals, hides out in the Casbah section of Algiers. He knows police will be waiting for him if he tries to leave the city. When Pépé meets Gaby, a gorgeous woman from Paris who is lost in the Casbah, he falls for her.

Pierre Gilieth has committed a murder in Paris. He flees to Barcelona, where he runs out of money. So he joins the Spanish Foreign Legion. He meets there two fellow countrymen, Mulot and Lucas. He tries to forget his fault... but Lucas's friendship soon appears to be less unselfish...