THE HERMIT OF GORDON’S CREEK
The disappearance of two airmail pilots leads to a mystery that centers about an abandoned mine and a strange old man.
KIDNAPPED IN THE JUNGLE
A hint of buried treasure in the ruins of an old French mission leads Hal deep into the Central American jungle.
THE COPPERHEAD TRAIL MYSTERY
Baffling and blood-curdling events center about the ranch where Hal Keen and his friends had gone in search of gold.
THE LONESOME SWAMP MYSTERY
The lonely and mysterious swamp gave up its secret only after a series of terrifying events taxed Hal’s courage and ability.
THE CLUE AT SKELETON ROCKS
In this new thriller Hal Keen finds mystery and adventure in and about a lonely lighthouse on Skeleton Rocks, off the Maine coast.