Frank and Joe Hardy solve the mystery of sabotage.

Frank and Joe set out on a search for the men who kidnapped their father and for the dossier of an ex-convict that was stolen from him.

Frank and Joe Hardy are determined to bring to justice the vicious criminals who kidnapped their detective father while he was investigation sabotage of a road-

A sleek new hydrofoil is scheduled to start ferrying passengers between Bayport and Cape Cutlass. But business enemies of the hydrofoil owner have stirred up a