In 1977, the middle-class Trentons move from
New York City to
Castle Rock,
Maine. In the summer of 1980, Vic learns that Donna has recently had an affair with local tennis player Steve Kemp. In the midst of this household tension, Vic's advertising agency is failing due to a scandal over a cereal. Vic is forced to go on a business trip, leaving Donna and their son, four-year-old Tad, at home alone. Joe Camber is a blue-collar mechanic who abuses his wife, Charity, and their ten-year-old son, Brett. Charity wins a $5,000 () lottery prize and uses the proceeds to bargain with Joe to allow her to take Brett on a trip to visit Charity's sister in
Connecticut and show him the possibility of a better life. Joe agrees and secretly plans to take a pleasure trip to
Boston with his friend Gary Pervier, an alcoholic war veteran. The Cambers' dog Cujo, a large, good-natured
Saint Bernard, chases a rabbit in the nearby wilderness and inserts his head in a small cave. A
bat bites him on the nose and infects him with
rabies, against which Cujo has not been
vaccinated. Cujo enters the
prodromal phase, becoming lethargic and irritable. After Charity and Brett leave town, Cujo kills Joe and Gary. Donna, with Tad, takes their failing
Ford Pinto to Joe's house for repairs. The car breaks down in the Cambers' dooryard, and as Donna attempts to find Joe, Cujo attacks her. She gets back into the car but becomes trapped when Cujo continues to attack them. The interior of the car becomes increasingly hot in the summer sun. During one escape attempt, Donna is bitten in the stomach and leg but manages to escape back into the car. Tad becomes catatonic with fear and begins to have
seizures. Steve goes to the Trenton home to attack Donna after she ends their affair and ransacks the empty house. Vic returns to Castle Rock after failed attempts to contact his wife. The police suspect Steve of kidnapping Donna and Tad. Sheriff George Bannerman is sent to the Cambers' house, but Cujo attacks and kills him. After witnessing the attack and realizing Tad is in danger of dying of
dehydration, Donna battles the weakened Cujo, with the animal seemingly winning before she bludgeons and stabs him in the head with the remains of the baseball bat. Cujo slumps over, dead. Vic arrives as the fight ends, but Tad has already died from dehydration and
heatstroke. A veterinarian performs a necropsy on Cujo to check for rabies prior to the cremation of his remains. Charity receives a phone call speaking about the deaths of Tad and her husband due to Cujo's rampage. Several months later, the Trenton and Camber families are trying to move on. Donna completed her treatment for rabies, and her injuries healed. The Trentons' marriage has survived, as well as Vic's business, and they mourn Tad together. Charity, now working in order to support herself and Brett, gives her son a new, vaccinated puppy. In
postscript, it is said that the hole Cujo chased the rabbit into was never discovered, and the bats abandoned it. It also reiterates to the reader that Cujo was a good dog who always tried to keep his owners happy, but the ravage of rabies drove him to violence. == Characters ==