Dink and his friends unearth the mysterious truth behind the envelopes incorrectly delivered to his house.

Nancy's sympathy for a pair of adopted twin babies leads her into a surprising mystery.

The Alden family rents a houseboat to drift down the river, and encounters a mystery in the little towns along the river, involving a fast black car.

When he finds a torn piece of paper with only part of a word on it, boy detective Nate sets out to find the missing pieces.

While solving the mystery of an old man's disappearing fortune, Nancy ends a family feud and reveals the identity of an orphan of unknown parentage.

Nate the Great solves the mystery of the missing picture.

Dink, Josh, and Ruth Rose investigate a mysterious man in black who Josh believes is a vampire.

Frank and Joe race against time to retrieve a scientist’s top-secret invention before thieves get their hands on it. But the young detectives soon discover that they are involved in a mystery far greater in scope than just safeguarding the invention. When Joe is kidnapped, this incident starts Frank of on a chase that could end disastrously for him and his pals.

A fifth-grader with a photographic memory and her friend Eric help solve the mystery of the stolen diamonds.

The ten-year-old detective continues his war on crime in Idaville through ten more cases, for which the reader is invited to guess the solution before it is revealed.