The Incredible Mr. Limpet

September 1941 just before the attack on Pearl Harbor. Henry Limpet, a shy bookkeeper, loves fish with a passion and wishes he could be one. His friend George Stickle is a machinist’s mate in the United States Navy. Limpet's wife Bessie is fiercely patriotic and Limpet tries to enlist but he is rejected, classified as 4F because of his poor eyesight and other reasons.

After the attack on Pearl Harbor, Limpet directs a Navy convoy to a nearby German U-boat. Limpet gets himself commissioned by the Navy, complete with an advanced rank and a salary, which he sends to Bessie. He helps the Navy locate Nazi U-boats by signaling with his "thrum", and plays a large part in the Allied victory in the Battle of the Atlantic.