Age Group: 9 - 12 Years

Description:

In the seventh Hardy Boys mystery, Frank and Joe Hardy take on two cases that turn out to be one. Mary Todd asks the Hardys for help in finding her brother, Professor Morgan Todd of Kenworthy College, who has vanished without a trace, while their detective father Fenton Hardy is investigating sabotage at a brand-new Coastal Radar Station. A puzzling message scribbled on an exam paper sends the boys first to the college, where the professor's nervy colleague Cadmus Quill behaves very strangely. Soon Frank, Joe and their pals Chet and Biff find themselves camped out at the rugged Honeycomb Caves, dodging a hot-tempered hermit, an exploding metal detector, a burning boathouse and a mysterious submarine slipping in and out of the cliffs. Behind it all lies a daring underground plot — and the startling secret of the caves themselves.