This is the war and everybody in Germany should beware : the enemy is listening. One family in particular had better be even more careful than the average citizen of the Reich : the Kettwigs. Indeed they own an armament factory and their engineers, technicians, workers and of course themselves belong to a highly sensitive sector. They are under the constant scrutiny of those who want to get hold of the secret weapons devised in the plant, notably of a wire which, when attached to a balloon, may become the most effective anti-aircraft ever. For sure, they should distrust everybody. Isn't Nolte, the waiter, an enemy agent? Should young Bernd Kettwig allow himself to be seduced by this pretty woman ? As for Bernd's secretary, is she right when she lets this handsome man woo her?