A plot to steal a top-secret instrument vital to the United States space program poses a challenging case for Frank and Joe Hardy. After rescuing a South Americ

Beset by an enemy from within, Dan searches for the gypsies he once knew in York and is led inexplicably into a calamity involving the Black Death in a hostile

Frank and Joe solve the mystery of the secret locked room in the spooky Dalrymple Mansion.

The search for a missing boat leads Frank and Joe, the Hardy boys, down to Mexico where they encounter a tribe of Indians.

When a freak natural phenomenon dissolves the boundaries between yesterday and today, the world is transformed into a patchwork mixture of the present and the d