Hardy Boys 04: The Missing Chums

Two of the Hardy Boys's chums take a motor trip down the coast. They disappear and are almost rescued by their friends when all are captured. A thrilling story of adventure.
Not only is the local bank robbed, but two of the Hardy boys' pals mysteriously disappear after a masquerade party. Are the events related? How the Hardy boys use all their courage and skill to outwit the criminals provides an exciting climax to one of the most baffling mysteries the young detectives have ever encountered.