While running from an SID officer, the Earthlings are spotted by two giant children, who, whilst chasing them, fall down a concealed well and become trapped. The giants try to dig them out, but a cave-in thwarts their efforts. After Inspector Kobick captures Steve and Dan, Valerie and Betty go to the parents of the children and offer to help them if they will convince Kobick to release their friends. After some prodding, Kobick puts duty aside and allows Steve and Dan to help in the rescue, with no deal to set them free. In the meantime; Mark and Fitzhugh find another way into the well, and try to slip their friends out past Kobick.
The little people come to the aid of two giant children who are trapped underground after a cave-in.