Reunited in the Legion, the Geste brothers have made two good friends, the Americans Hank and Buddy, and one dangerous enemy-the sadistic and tyrannical Sgt-Major Lejaune.

Sergeant-Major Lejaune now believes Beau is carrying a valuable jewel, and is determined to have it. A first attempt at theft is a failure. Then Lejaune announces that the squad is to be posted to Fort Zinderneuf, where the Geste brothers will be in his power.

Worn out by the strain of life at Fort Zinderneuf and by his struggle against alcoholism, Captain Renouf has committed suicide. Now Sgt-Major Lejaune is in sole command.