Nathan Bronfman (TIM ROBBINS) is a research scientist whose formal and strict upbringing regarding his table manners years ago at the hands of his parents (ROBERT FORSTER and MARY KAY PLACE) led him to attempt to teach the same to ordinary mice.
Lila Jute (PATRICIA ARQUETTE) is a woman whose excessive hairiness eventually led her to move into the woods and become a best-selling nature writer. Yet, when she turns thirty and her hormones start calling, she decides she must "fit in" with how "normal" women look and thus visits Louise (ROSIE PEREZ), an electrolysis technician who removes her hair and fixes her up with Nathan.
The two immediately hit it off despite their idiosyncrasies and Lila's hiding of her hairiness from Nathan. Their lives change, however, when they come across a feral man (RHYS IFANS) living in the woods who was raised by a man who thought of himself as an ape. Believing he can "save" this man that his assistant, Gabrielle (MIRANDA OTTO), names "Puff," Nathan sets out to condition him to be a civilized human.
Yet, his attention paid to Puff and Gabrielle -- who's obviously interested in her boss in more than just a professional way - puts a strain on his relationship with Lila. As things progress along with Puff's rapid learning curve, they eventually go out of control, leading to the various characters having to deal with the many facets of human nature, including murder.