Relates the exploits of the four Alden children as they locate a missing man. "Henry, Jessie, Violet, and Benny used to live alone in a boxcar. Now they have a home with their grandfather and are determined to solve the mystery that surrounds an old yellow house on his property. Strange things have happened in that house where long ago a man disappeared. When the Boxcar Children explore the house, they find an old letter written by the brother of...

The children are spending the summer on their own private island but there is a mysterious stranger on the island.

The Boxcar Children, now living with their grandfather, spend the summer on their Aunt Jane's ranch. Their aunt seems quite unhappy until at the end of the summer a surprise discovery brings happiness to all

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 investigate various mix-ups at a zoo run by their grandfather's friend in an effort to save it not only from pranksters but also from the town council

While on a camping trip with their grandfather, the Alden children try to find out about the loud music and missing food that threatens to scare away other campers

While helping run Jerry Taylor's general store, the Alden children investigate his mysterious employee Nancy

The Alden children have another mystery to solve when they visit a castle and must figure out which of the guests has stolen the Stradivarius violin.

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

At the same time that the Alden children's efforts to raise money for a new hospital wing are being sabotaged by nasty tricks, they find their attempts to befriend the new girl Beth frustrated by her strange behavior