Meet Ben and Flo Healy! They want a young child of their own, but Flo is incapable of having a child herself. Enter Junior, a little monster who has been to foster parents' homes since he was a baby and always made himself get thrown out so one day he goes to the orphanage and causes trouble for the poor nuns (although some of them deserved it). So Ben and Flo go to adopt a child and the administrator, Peabody, cons them into taking Junior off their hands. Junior goes home with the Healys to a nice house which includes a bedroom full of clowns! Ben takes an immediate love to his son, no matter what the horrible things he does, even though he injured his grandfather, a bigoted politician, really turned a birthday party into a "blast", sicks a bear onto campers on a camping trip, and even goes on a joyride with convicted killer Martin Beck!