Cujo

Donna Trenton (Dee Wallace-Stone) is a frustrated suburban housewife whose life is in turmoil after her husband learns about her having an affair. Brett Camber (Billy Jayne) is a young boy and a son of a mechanic (Ed Lauter) whose only companion is a St. Bernard named "Cujo." Cujo is bitten by a bat with rabies and his behavior begins to change. When Donna and her young son Tad drive out to the home where Cujo and his owners live, the gentle Cujo has been driven insane by rabies and has killed one of his owners. Worse, their car gives out near the mechanic's house, and Donna and Tad are trapped inside while the massive dog waits outside, attacking repeatedly.