Spies Karl and Lilly target the German Kettwig company, trying to secure data about an innovative tearproof wire. Bernd Kettwig is wooed by Lilly while his assistant Inge falls for Karl, and two other employees are coerced into treason.

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?—Guy Bellinger