Henry, Jessie, Benny, and Violet Alden meet Mike Wood and a strange chain of events begins. Mike's house is mysteriously burned down, a man in a blue hat appears, and the Alden's uranium mine is in danger of being sabotaged. The four youngsters solve the mystery.

The Alden children and their grandfather are hiking down from Flat Top when a rockslide reveals a cave with a big secret.

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

A summer spent in doing light housekeeping in a lighthouse proves to be a happy and adventurous time for the Boxcar children, as well as for their neighbor, Larry Cook, who does not want any friends.

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.

The Alden children save an old woman's house, land, and all the animals in her animal shelter from greedy contractors.

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.

While spending their winter vacation at Snow Haven Lodge, the Boxcar Children sign up to compete in the snow events. But no sooner has the competion begun, than the children have a mystery to solve!

The Boxcar Children are spending their vacation on a farm. They learn to do everything from milking cows and making homemade jam to raising a barn. Then one day they spot a beautiful horse locked up in a stable. Who is the mystery horse? And why is it hidden?

The Aldens investigate when an old wooden mask they have found is stolen.