Next in the Privateersmen mysteries, they find themselves imprisoned in New Orleans (then under Spanish rule) for a piratical attack that they chanced upon the remnants of and told the authorities about.
The plot deals with their working out what the story behind the attack was while being (gently but firmly) kept under surveillance.
It's a good story, although perhaps a little wilder than some of the others. According to the author, one of the more outlandish aspects is true, however. So maybe this kind of thing did happen.