Henry, Jessie, Violet and Benny Alden are brothers and sisters - and they're orphans. The only way they can stay together is to make it on their own. One night, during a storm, the children find an old red boxcar that keeps them warm and safe. They decide to make it their home.

Henry, Jessie, Benny and Violet Alden discover that a mystery surrounds the run-down yellow house on Surprise Island. The children find a letter and other clues that could lead them on the trail of the man who vanished from the house.

The Aldens set out to prove the innocence of their old friend Mike who has been accused of starting a fire.

A family, snowbound in a vacation cabin, discovers adventure in surrounding wild life, three children they find in the snow, and a search for a lost recipe.

The Alden children travel on a Mississippi paddle-wheel steamer to visit an old family friend in his cabin near Hannibal, Missouri, and try to discover who is responsible for the mysterious activities near the house.

When their favorite pizza restaurant almost goes out of business, the Alden children try to help their friends stay open while they find out who is behind all their problems.

There are many legends about a woodshed near the old farmhouse where the Alden children's grandfather grew up.

"The Aldens are making the journey to their Aunt Jane's house for an overnight bicycle trip. On their first night, though, the children are caught in a rainstorm. They have to take shelter in an old, abandoned house. There, a most unusual mystery--a lost dog--finds them! Can the boxcar children figure out the mystery of where the dog belongs?"--P. [4] of cover.