In both the novel and the 1983 movie adaptation of "Cujo," it's established that the primary reason for Cujo's transformation from a kind-natured, family-friendly dog to a maniacal, murdering wild animal is because Cujo has become infected by rabies. However, there are moments in King's original novel that hint Cujo's grisly personality change might also be the result of something far more sinister.
In the book, King alludes to a local serial killer active in the fictional town of Castle Rock, Maine, prior to the events of "Cujo." This killer — Frank Dodd — was initially featured in King's 1979 novel, "The Dead Zone." After the police learned his identity through the novel's protagonist, Johnny Smith, Dodd died by suicide to escape prosecution, leaving a confession behind proving their suspicions about him correct.
Fans and publications have widely theorized that Dodd's spirit is actually possessing Cujo, twisting his mind and allowing him to continue his killing spree from beyond the mortal realm. While that theory is far and away the most popular explanation behind Cujo's behavior, there may also be another, even darker reason for Cujo's rampage as well.
In the book, Tad is haunted by some sort of supernatural presence in his closet as Cujo's mentality slowly deteriorates. What exactly is this supernatural force in Tad's closet? Is Dodd the one possessing Cujo, or is there some sort of larger evil entity pervading Castle Rock? Perhaps Dodd himself was merely the victim of this same paranormal evil, just as how Jack Torrance became a vessel for the ghosts in "The Shining."
If you or anyone you know is having suicidal thoughts, please call the National Suicide Prevention Lifeline by dialing 988 or by calling 1-800-273-TALK (8255).
