Cooper and his family have just moved from an apartment in Boston to a house deep in the woods of Maine. Cooper feels homesick and has a problem settling in, largely due to his tendency to be scared of everything. His feels lonely and misses his best friends in Boston, Gary and Todd.
He is bullied by his brother Mickey, who is three years older.
Cooper hears dogs outside on his first night in his new house and ventures into the woods the next day to prove their existence. In the woods he meets and befriends a girl named Fergie. Fergie plays a mean joke on Cooper when she first meets him, convincing him that his house and the woods surrounding his house are haunted. Fergie later admits that she did this at the request of Mickey. Cooper scares her back in retribution, and the two become friends. Cooper and Fergie try to come up with a way to scare Mickey to get back at him for all of the trouble he has caused Cooper.
Cooper is harassed by two ghost dogs throughout the book. He and Fergie eventually follow the dogs into the woods at their urging and are led into a shack called the Changing Room where the ghost dogs change bodies with Cooper and Fergie. They are told that the dogs used to be human and have had a curse laid upon them. They have been wandering the woods as dogs for a hundred years. By stumbling into the Changing Room, Cooper and Fergie allow them an escape.
As dogs, Cooper and Fergie try to convince Cooper's parents that they are the real Cooper and Fergie, but are unsuccessful. They eventually succeed in dragging the fake Cooper and Fergie back to the Changing Room, but two chipmunks entered the Changing Room before they got there, and they changed bodies with the chipmunks instead. The humans that inhibited the dogs remain in Cooper and Fergie's bodies and go home with Cooper's parents.
Cooper and Fergie exit the Changing Room as chipmunks and hunt for acorns.
Cooper has many freckles that stand out when he's scared. He has long hair that he wears to cover his big droopy ears.
Cooper's dominating personality trait is fear. He is scared of everything, and his fear causes him to see things that aren't there. He mistakes a garden hose for a snake and a bunny rabbit for a monster. Given his fear, Cooper is uncharacteristically brave, sneaking out at night and going into the woods to investigate ghost dogs he fears.
Cooper collects Snow Domes. He has a collection of 77 of them that he spends time cleaning, setting up, and admiring in his room.
Cooper is slightly obsessed with the baseball team, the Boston Red Sox.