Nancy responds to a friend's frantic call for help and she and her father travel to Crocodile Island with Bess and George to study the reptiles and try to uncover a group of poachers. Upon arriving, the group is kidnapped, but they escape and uncover a sinister plot involving many unsuspected victims.
This book reveals that George's real name is actually "Georgia," but that she hates being called by her actual name.
It's revealed that Bess's mother's maiden name is "Boonton," but it's never said if that's the maiden name of George's mother (it can be assumed that it isn't).
While it mentions in every single book that Bess and George are cousins (presumably first cousins), from this book, it can be assumed that Bess's father and George's mother are most likely brother-and-sister.