German nationalists financed by the great industrialists, and led by the sinister Lt Commander yon Horn of the German Navy, have other ideas. They wanted the area west of the Rhine to be re-incorporated into the Weimar Republic. To do this they plan a series of strikes against the Allied troops marching westwards, culminating by the attack of their "Hell's Angels".
These "Hell's Angels" are barnstorming ex-pilots of the German Imperial Air Force, who fled to America after the Great War. Daredevils to a man, they criss-cross the USA performing at air shows, circuses and the like. Now von Horn wants them back for the final attack on the withdrawing allies, which will change the face of Germany if it succeeds.
But he has not reckoned with his old enemy, Common Smith VC and the crew of the Swordfish. Alerted by "C", the mysterious head of the Secret Service, to what the German nationalists intend, it is the Swordfish's task to stop the Hell's Angels reaching Europe.