Alain Lefevre is a boxer paid by a Marseille mobster to take a dive. When he wins the fight he attempts to flee to America with the mobster's girlfriend Katrina. This plan fails and he seeks escape by joining the foreign legion.
As part of the legion he tangles with abusive lieutenant Steinkampf and bonds with legionnaires Luther, Mackintosh and Rosetti.
They are send to Morocco and assigned to defend a remote fort against the attacks of enemy Berbers. The mobster discovers his whereabouts and enrolls two hitmen to finish him off. With their fort under siege and enemies within, Lefevre finds that second chances are difficult to come by in the Legion.