Still reduced to the size of insects, Andrew, Judy, and the robot Thudd go to a pond, where they encounter dragonflies, moss animals, and fierce larvae in an attempt to learn why frogs are disappearing throughout the world.

After being shrunk by a shrinking machine, Alexander, his cousin Judy, and Thudd the robot encounter drain flies, a cockroach, and worse as they work their way through Mrs. Scuttle's house toward safety.