Based on a real story during WWII where Japanese naval soldiers met Italians who were in the submarine Comandante Cappellini used to transport strategic materials to and from Japan.

Wealthy young man Ramon Laredo is abducted and put into service aboard a ship commanded by a none-too-scrupulous smuggler. When the ship encounters the foundering "Lady Letty," some of the Letty's crew is brought aboard, including Letty 'Moran' Sternerson, feisty daughter of the Letty's captain. Moran and Ramon have little use for each other, but when trouble erupts and the smuggler Captain Kitchell turns his evil eye on Moran, it is Ramon who comes to her rescue.