The Shattered Helmet (The Hardy Boys, No. 52)

Danger is the name of the game when the Hardys agree to help their pen pal from Greece, Evan Pandropolos, search for a priceless, ancient Greek helmet. Years ago, Evan’s uncle had loaned it to Hollywood movie company for use in a silent motion picture, but the treasured helmet had been lost. Picking up foes along the way, the young detectives unearth clues that keep them constantly on the move—from their Greek college campus to California and finally to Greece.

• The Masked Monkey (Hardy Boys, No. 51)
• The Clue of the Hissing Serpent (Hardy Boys, Books 53)
• The Mysterious Caravan (The Hardy Boys, No. 54)
• The Witchmaster's Key (The Hardy Boys #55)
• Danger on Vampire Trail (The Hardy Boys, No. 50)
• The Bombay Boomerang (Hardy Boys #49) (The Hardy Boys)
• Hardy Boys 58: The Sting of the Scorpion (The Hardy Boys)
• The Firebird Rocket (The Hardy Boys, No. 57)
• Hardy Boys 56: The Jungle Pyramid (The Hardy Boys)
• Mystery of the Whale Tattoo (Hardy Boys, No. 47)