- Kurt Vogel, master criminal
- Professor Wesley Yule
- Otto Arnheim, a henchman
- Loretta Page, insurance detective
- Simon Templar, The Saint
- 'Orace, associate of The Saint
Locale: the coast of France
Synopsis: Simon Templar is visiting the French coast on his boat, The Corsair. One night a woman swimming approaches his boat, it is Loretta Page. She is a private detective for an insurance agency, investigating recent thefts of maritime salvage in which the thieves make off with assets from sunken vessels before salvage operations can commence.
Loretta has traced the thefts to Kurt Vogel on board the Falkenberg, and had been watching it. The Falkenberg is outfitted for deep sea recovery. Vogel has a guest, Professor Wesley Yule, inventor of a deep diving outfit called the "bathystol"; which Vogel wants.
The Saint and Loretta team up to infiltrate the Falkenberg.
Review: This thriller with The Saint, the beautiful woman, and the master criminal is somewhat predictable but still fun. The settings on the ocean are well done and descriptions bring us all the sights and sounds of the French coast. The love interest between Simon and Loretta is detailed much more than the later stories with Patricia Holm. Vogel is calm and cold, and focused on his treasure stealing empire. The finalé comes with The Saint and Vogel both diving to Vogel's undersea treasure trove. This is a pure thriller - no mysteries to be had. 'Orace lends a supporting role, Peter Quentin and Roger Conway make brief appearances.