"The Aldens visit the shore in New Jersey and help out at an amusement pier that is rumored to be unsafe"--

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.

The Alden children go to care for their Aunt Jane on her ranch and discover a new mystery as they try to bring her out of her doldrums.

A young Canadian visitor helps the Alden family solve a mystery involving a lost coin collection.

The Aldens try to help a visiting Russian gymnast who is surrounded by mysterious people and events and who seems to have a secret.

The Alden children hunt for their late grandmother's necklace that has been missing for years.

At an old library, the Alden children discover a boy who needs their help and a stranger who is after a valuable object they found in the library.

The Alden children help out a storeowner at the Hope Harbor Mall and discover that someone is tampering with the merchandise shipments.

"The winter sports season is here, and the Aldens are excited about all the snow activities--especially snowboarding. But soon they find themselves in the middle of a mystery surrounding a star athlete and a stolen snowboard"-- Provided by publisher.

The Aldens help out at a minor league stadium and investigate when it appears someone in the ballpark is stealing the home team pitcher's signals and relaying them to the batters of the other team.