One warm night four children stood in front of a bakery. No one knew them. No one knew where they had come from.
Henry, Jessie, Violet, and Benny used to live alone in a boxcar. Now they have a home with their grandfather, and are taking a vacation at a cabin in the woods!
When the Aldens arrive at Lake Lucille, they're excited to explore the forests and lakeside paths. Soon, rumors begin spreading about a monster in the lake. The Aldens meet a scientist who has been studying lake monsters. One night, when they hear strange noises outside, they wonder -- is there really a monster in Lake Lucille? It's up to the Boxcar Children to find out!