Something sinister is taking place in the Sahara. The inhabitants of an Arab village are carried away to slavery; then Fort Allengrah, a French Foreign Legion base, disappears from the face of the earth along with its inhabitants. Captain Hugh Radford, a British special agent working with Interpol, is given a temporary commission in the Foreign Legion, with an American airman and a French ballistics expert. Outnumbered, cut off from help, and almost unarmed, Radford and his two companions must fight to save the whole free world.