Explosions thundered in the territory occupied by the Nazi invaders. An old and experienced military leader, Admiral Reingardt, arrives to investigate this incident. Together with the chief of the Gestapo, Standarfenführer SS Hübe, he takes all measures to suppress the activity of the partisans, raids and arrests, but all in vain. Subversion continues under water. To fight the bombers from Italy send a detachment of soldiers who have experience of underwater war.