Donna Trenton (Dee Wallace) is an unhappy housewife in Castle Rock, Maine, her life in turmoil after her husband discovers her affair. Brett Camber (Billy Jayne) is a boy, the son of a mechanic named Joe (Ed Lauter), whose only companion is a St. Bernard named Cujo. The dog is bitten by a rabid bat and deteriorates quickly. Brett and his mother leave for Connecticut to visit an aunt. When Donna and her son Tad (Danny Pentauro) visit the mechanic’s home to get their car fixed, the gentle dog has been driven insane by the rabies and killed Joe and a neighbour. The car battery dies, and Donna and Tad are trapped inside.
The dog slaughters anyone who comes to the house, including the local sheriff, George Bannerman (Sandy Ward). Donna makes a break for it and is attacked by the dog. After a brutal struggle, she beats Cujo with a baseball bat and when the bat breaks, she stabs the dog with the sharp end. She revives her son, who passed out in the hot car. Cujo tears through the kitchen window and attacks them. Donna shoots it with the sheriff’s revolver just as her husband arrives. This differs from the end of the book, as is common, and there appear to be alternative endings to the film.
The film was directed by Lewis Teague from a script by Don Carlos Dunaway, Barbara Turner, and Stephen King, from his 1983 novel. Most of the movie’s power comes from the transformation of a big, sloppy, lovable dog into a slavering monster and the family’s horror at the transformation. Dee Wallace is a mother transformed into a horror-movie hero. Danny Pintauro as Tad is heart-breaking as a terrified child.
The vocalizations of Cujo himself are created by Frank Walker, who voiced Fred in Scooby-Doo. There is nothing supernatural or otherworldly about the monster. It’s an ordinary dog with an ordinary disease. Mom against Dog has been compared to Ripley versus the Alien and Sarah Conner versus the T-1000. The battle has been described as primal, ugly, and glorious. The film won the 1982 British Fantasy Award.
Four St. Bernards and a Black Lab in costume, a mechanical dog, and a stuntman in a dog-suit brought Cujo to life. The dogs had to have their tails tied down or they would wag them happily while growling and slathering like a monster. The real villain, perhaps, is the stupid Ford Pinto. Stephen King said he was inspired by a trip to the garage for his motorcycle, where he was threatened by a big dog, and by a Ford Pinto piece of shit car.