Dietrich is presented with an old scrap of parchment which shows an ancient water source deep in the desert. Allied intelligence sends Moffitt to find the map before it can be translated; he must get it by masquerading as a German and Troy has orders to shoot him should he find the information (and destroy it) but then not be able to escape. Which is, of course, exactly what then happens. Troy must face the decision of killing his comrade -- and friend -- or finding someway to disobey the orders and rescue the mission.