Description
The Submarine Caper
On a visit to Germany, the Hardy brothers investigate the theft of plans for a newly invented submarine and the mysterious disappearance of valuable coins and paintings.
The Four-Headed Dragon
Found dazed and incoherent in the woods, Mr. Hardy's assistant is then kidnapped from the hospital, and the Hardy boys pick up the trail of a vicious gang.
The Infinity Clue
After receiving a mysterious message from their father, Frank and Joe go to Washington, D.C. and become the target of terrorists.
ISBN:9780006929109
