A widowed field mouse must move her family -- including an ailing son -- to escape a farmer's plow. Aided by a crow and a pack of superintelligent, escaped lab rats, the brave mother struggles to transplant her home to firmer ground.

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.