Not knowing the kids are in the attic, Wayne heads up there to clean up. He unintentionally puts them out by the curb in a trash bag. When Wayne and his wife, Diane, cannot find Amy and Nick, they realize what has happened. They spend the rest of the movie searching for the kids. The Thomspons just chalk it up to Wayne's zany antics at first, but realize that Russ and Ron have also been shrunk.
While the adults frantically search for them, the kids make their way home to reverse the effects of the shrink ray. At less than an inch tall, the backyard is vast and wild, full of unknown and unexpected dangers. Something as harmless as the lawn sprinklers can be life-threatening. Their adventurous journey teaches them how to be strong and how to work together.