While on a camping trip, Ted Kerasote met a dog—a Labrador mix—who was living on his own in the wild. They became attached to each other, and Kerasote decided to name the dog Merle and bring him home. There, he realized that Merle's native intelligence would be diminished by living exclusively in the human world. He put a dog door in his house so Merle could live both outside and in.

A deeply touching portrait of a remarkable dog and his relationship with the author, Merle's Door explores the issues that all animals and their human companions face as their lives intertwine, bringing to bear the latest research into animal consciousness and behavior as well as insights into the origins and evolution of the human-dog partnership. Merle showed Kerasote how dogs might live if they were allowed to make more of their own decisions, and Kerasote suggests how these lessons can be applied universally.