Lee Cato is an American who joins the French Foreign Legion in search of a killer. He is befriended by Sasous, an ex-criminal from the Paris underworld, who knows how to work the grapevine and get information. He helps Cato in his search, but there is always the Legion to contend with and it is fully demanding. There is the strict discipline, the tough, sadistic Sergeant, the ambitious young Lieutenant and the guerrilla war in the fierce heat of East Africa. This is how the Foreign Legion live, the way they fight and the way they die.