Before they were cursed to haunt the woods of Maine, the ghost dogs were once a pair of human friends. Human, that is, until an evil spell was cast on them, one that turned the friends into ghostly hounds. For centuries, the two roamed, looking for a chance to regain their human forms. When Cooper Holmes and his family moves into a house deep in the woods, the ghost dogs finally get their chance.
Late at night, the easily scared Cooper is kept up by the sound of barking. Not a single dog is in the area, but he keeps finding pawprints just outside his house. Cooper knows something strange is going on, but nobody seems to believe him. When Cooper meets a neighbor girl named Fergie Ferguson, the two become fast friends. Together, they try to solve the mystery of what's going on, but soon find themselves face to face with the ghost dogs. The creatures lure them into the Changing Room, a shack in the woods capable of body-swapping anyone inside. With their targets finally trapped, the ghost dogs' plan is a success. They now have the bodies of Cooper and Fergie, while they are now trapped as dogs.
However, this success does not last. At the dinner table, Cooper's out-of-character behavior alerts his family that something is wrong. In their dog forms, Cooper and Fergie try to tell the Holmes family what has happened. Unfortunately, nothing seems to work, forcing the two to lure their impostors back to the Changing Room, trapping them all in once more
With the swap reverted, the ghost dogs wander out of the shack and back into the woods.
The television adaptation of the book depicts the ghost dogs as being bandits prior to their transformation, which is caused by a magical tree, rather than the Changing Room.
The ghost dogs' main goal is to revert back to their human forms, they will target anyone if it means getting their bodies back.
The ghost dogs are described as looking similar to black labs, only also having glowing red eyes.