When kids sneak into inventor Wayne Szalinski's upstairs lab to retrieve an errant baseball, his experimental shrink ray miniaturizes them. When Szalinski returns home, he destroys the device which he thinks is a failure and dumps it in the trash, throwing out the kids along with it. The four children must survive the journey back to the house through a yard where sprinklers bring treacherous storms and garden variety ants stampede like elephants.