Both parents must cope with the death of their child, Tad at the end of the book after Tad dies of heat exhaustion in the car where he and his mother are trapped. Cujo operates on both the ordinary and the extraordinary, in terms of its levels of horror. On one hand, unlike most of Stephen King's novels, Cujo is not dependant upon the supernatural to inspire terror in its reader. In the real world, people are attacked and are killed by dogs. Rabies is a real illness. The horrific thing is that once Cujo was a beloved family pet, but because of the fact he has contracted rabies, it as if he has become possessed by a demon and he becomes a killer. The ordinary, beautiful setting of a quiet suburb that seems ideal to raise one's children makes the horrific contrast between Cujo's actions and the setting particularly effective. The beginning of the novel is also horrific for any animal lover to read, as it is told partly from the point-of-view of Cujo...

Cujo's thinking becomes increasingly frightening as the disease begins to eat away at his central nervous system, and the reader is forced to see the human characters through his distorted perspective.
Towards the end of the novel, when Donna and Tad are trapped in the car, the novel operates on a level of claustrophobia, as the two of them cannot escape -- and again, being trapped in the family car is horrific, because the familiar becomes a place of horror. The two are reduced to the barest elements of survival, as they struggle against fear, hunger, and the heat, as well as the animal that is threatening their lives. And the final, realistic rather than supernatural climax of the novel is when Tad dies. The death of a child is another example of realistic horror that seems justified within the plot of the novel, but strikes a profound contrast between the setting and the initial expectations it creates in the mind of the reader.