The Preposterous Adventures of Swimmer — Alexander Key

After years in captivity, a brilliant otter escapes into the wild

Growing up in the high country, Swimmer bathed in clean water and dined on fresh crawfish. Then the trapper came, killing Swimmer's mother and imprisoning him and his sister, who did not survive. After years of being poked and prodded by the Professor, he has had enough. He slips out of the townhouse and into the park across the street but is forced to return home when the city water proves too filthy to swim in. Unable to proceed on his own, he does something he vowed never to do: He asks the caretaker, Clarence, for help.
 
Convinced that Swimmer would die in the wild, Clarence refuses to help the otter break free. And so, when the Professor is on a trip to Nashville for a lecture, Swimmer takes his chance, escaping back into the high country. It's a wild world out there, and this clever otter intends to conquer it all.