Mystery of the Lake Monster

The Aldens find evidence that the stories about a monster in Lake Lucille might be real.
The Aldens are spending a week at a lodge on a lake in the Adirondack Mountains in New York State.

Carl Nielson, who lives in the mountains with his dog, Wildman, tells the Boxcar Children about "Lucy", the monster who lives in the lake. Nora, the owner of the lodge, quickly dismisses Carl's story and insists that the monster does not exist. But then the Boxcar Children hear weird noises coming from the lake and find a huge monsterlike footprint in the sand. They have another mystery on their hands!