Relates the exploits of the four Alden children as they locate a missing man. The Boxcar children travel to Maine, take canoes into the wilderness and live in a house exactly like the one on Surprise Island, except the Maine house is brown, not yellow. They then untangle the mystery of the two houses.

Henry, Jessie, Violet, and Benny Alden are on another summer trip to visit Aunt Jane at Mystery Ranch. They're thrilled to find their friend Mike Wood lives in the bustling new town near the ranch. But one night, Mike's house burns down and he is blamed for starting the fire!

A family starts out on a one-day mountain climbing excursion that becomes very exciting. In fact, it becomes an adventure for the former "boxcar" family. They unearth some mysteries and have a fine time in the process.

When the Alden children and their grandfather visit Everglades National Park in Florida to solve the mystery of a missing ranger, they discover that a panther provides a clue.

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 Aldens spend the summer on their aunt's ranch! The ranch is a beautiful place, but it's also the source of trouble between Aunt Jane and Grandfather. As the Boxcar Children explore the land, they make an amazing discovery. Will it help mend Aunt Jane and Grandfather's relationship?"--Publisher's description.

When the Aldens go to the Pickering Natural History Museum to assist with the opening of a dinosaur exhibit, their work is hampered by a series of mysterious happenings.

The Boxcar children investigate the disappearance of a student's research paper from an observatory and the subsequent disappearance of another student.

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