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.

The Alden children suspect someone of trying to sabotage the local dog show.

While on a cruise with their grandfather, the Alden children help discover who is behind the mysterious troubles of the ship--disconnected phone lines, engine trouble, a man overboard--and still have fun sightseeing, eating, and swimming.

While staying at a hotel in New York City, the Aldens investigate a series of annoying pranks plaguing the management and guests.

While helping fix up the old house their cousins have bought, the Aldens hear stories about its being haunted and find evidence suggesting that there may be a ghost there.

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.

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.

The Boxcar children investigate when ice cream and other items start disappearing from their favorite ice cream parlor.

The Aldens search for carousel horses that have disappeared from an amusement park.