Eccentric Aunt Jane needs help on her ranch so the Aldens, affectionately known as the boxcar children, get help from a private detective.

When the Aldens stay at an old Kansas inn, Harry, Jessie, Violet, and Bennie try to figure out why guests travel great lengths to visit it.

While visiting Lake Lucille in the Adirondack Mountains, the Aldens hear stories about a monster in the lake and then encounter evidence that it may be real.

When the Alden children go camping on Blizzard Mountain, a place said to be inhabited by a ghost looking for buried treasure, they begin to think someone or something is trying to scare them off.