Mayhem is unleashed when a mischievous chimpanzee pours a potent youth serum into the water system, causing the hapless chemist who developed it to regress to childhood, along with his wife, boss and secretary. Comedy, starring Cary Grant, Ginger Rogers, Charles Coburn and Marilyn Monroe.

Research chemist Barnaby Fulton works on a fountain of youth pill for a chemical company. One of the labs chimps gets loose in the laboratory and mixes chemicals, but then pours the mix into the water cooler. When trying one of his own samples, washed down with water from the cooler, Fulton begins to act just like a twenty-year-old and believes his potion is working. Soon his wife and boss are also behaving like children.