Franklin W Dixon

When Mr. Hardy disappears while investigating a mystery surrounding a vacant house rumored to be either haunted or an abode for criminals, Joe and Frank search for the truth.

Frank and Joe unravel two mysteries, one involving a counterfeiting case and the other concerned with a national security case their father is working on.

On an ice-bound, snow-covered island, Frank and Joe attempt to solve the mystery of a boy's disappearance and the theft of a priceless collection of antique medals.

When their detective father asks them to play burglar in order to protect a client's valuable invention from thieves, the Hardy boys find themselves involved in a large and dangerous conspiracy.

The Hardy brothers interrupt their investigations of jewelry-store holdups to answer a plea from their cousin on a New Mexico cattle ranch.

When the Hardy Boys set out to solve the mystery of their missing chums, they discover a gang hide-out in a cave on an island along the way.

The search for a stolen boat leads the Hardy brothers to Mexico where they become involved with a band of Indians and a strange smuggling operation.

The attempted theft of a secret experimental motor and the kidnapping of a famous race horse are involved in a case of mysterious race car accidents that Frank and Joe are investigating.

Through the course of the mystery they are confronted with the theft of the Jeweled Siva, a valuable Oriental idol; an innovative hydrofoil speedboat; a terrified wealthy businessman and a health farm run by a mysterious doctor.

When Frank and Joe investigate threatening notes and a secret room in an old mansion, robbery and mistaken identity complicate matters.