This movie is a dramatization of the autobiography "Animals Are My Hobby" of Mrs. Gertrude Lintz a soft-hearted, 1920s New York socialite.

Buddy is the true story of Gertrude “Trudy” Lintz (Rene Russo), a progressive eccentric who helped change the public perception of apes when she raised a baby gorilla as her child.

On her New York estate, Trudy, her physician husband (Robbie Coltrane) and her assistant (Alan Cumming) care for a menagerie including four chimpanzees, whom she treats as her children: She teaches them table manners, to play croquet, mix martinis and do light housework. And they become the stars of Chicago’s 1933 World’s Fair. But her gorilla, Buddy, is her favorite.

She saves the sickly animal from death, and proceeds to raise him as if he were her own. But Buddy inevitably grows up, and it becomes increasingly difficult for him to fit into his human world. Finally, Trudy has to make the decision all mothers face - she has to let go.