Frank Carlson Library

When the children uncover a strange puzzle in a friend's back yard, it's the start of a "spy game" leading to gold. But first they must make sense of an old photo and a riddle, and learn just who is behind this mystery within a mystery.

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

Someone is trying to put Aunt Jane's motel out of business, but the Alden children aren't going to let that happen.

The Alden children, isolated in a storm at a small bus station, are led into a mystery centering on a polluted river.

While visiting the seaport town of Ragged Cove, Massachusetts, the Alden children find the ship's log of the Flying Cloud, shipwrecked in 1869, supposedly during a mutiny.

The adventures of the Alden family as they ride across country in a caboose that has a strange history---or is it a mystery?

The Aldens, while testing the latest version of their favorite computer game, are surprised to find messages directed specifically at them.

While spending two days touring a zoo to see the baby animals, the four Alden children, aged six to fourteen, help catch an escaped monkey, participate in a photography contest, and investigate a missing camera.

While canoeing and backpacking near Timberwolf Lake, the Aldens receive strange warnings to stay away from the area and stumble upon clues to a missing cache of stolen coins.

When the Alden children go camping on Blizzard Mountain, a place said to be inhabited by a ghost looking for buried treasure, they begin to think someone or something is trying to scare them off.