39 books in series

Hardy-guttene

Hardy-guttene is a 39-book series with 39 primary works first released in 1920 with contributions by Franklin W. Dixon, Jerrold Mundis, and Leslie H. Morrill.

The Tower Treasure
The House on the Cliff
Cover 7

The Secret of the Old Mill

The Missing Chums
Hunting for hidden gold
While the Clock Ticked
The Hidden Harbor Mystery
The Secret Warning
The clue of the broken blade
The flickering torch mystery
The Secret Panel
The sign of the crooked arrow
The Wailing Siren Mystery
The Yellow Feather Mystery
The Secret of Pirates' Hill
The Clue in the Embers
The Ghost at Skeleton Rock
Mystery at Devil's Paw
The mystery of the Chinese junk
Mystery of the Desert Giant
The Viking Symbol Mystery
The mystery of the spiral bridge
Footprints under the window
Mystery of the Whale Tattoo
The great airport mystery
The Bombay Boomerang
Masked Monkey
The Shattered Helmet
The Mysterious Caravan
The Witchmaster's Key
The Firebird Rocket
Mystery of Smugglers Cove
The Vanishing Thieves
Track of the Zombie
The Voodoo Plot
Tic-Tac-Terror
Trapped at Sea
Game Plan for Disaster
The Crimson Flame