In this exciting installment, after rescuing a woman from drowning the Hardy boys find themselves helping their father in the hunt for her missing brother. Along with their chums, they encounter a number of colorful characters as well as natural impediments in their quest. There is the crook who tried to steal one of their motorcycles, and a strange older man who tells the tallest tales they've ever heard. Between having their supplies stolen, Frank falling into a pit, and trying to survive in the caves, there is plenty of adventure in this exciting chapter in the lives of The Hardy Boys!