Four-year-old Tad Trenton has been having night terrors. Each night, a horrifying beast with glowing red eyes eases growls from within his closet that he will have him soon. Though his parents reassure Tad that no monsters can get him, they cannot explain why the closet door is found unlatched each morning. Nor can they keep their own adult fears, from a business crisis to infidelity, from threatening to tear their happy home apart.

Cujo is a two-hundred-pound Saint Bernard and the best friend that ten-year-old Brett Camber ever had. But when Cujo pursues a rabbit into a hole and gets bitten by a rabid bat, the once-friendly dog is suddenly turned into a crazed, unstoppable monster.

One fateful weekend, when the Cambers are on vacation and Donna Trenton's husband is out of town—again—Donna drives her car to the Cambers' garage for repairs. There she is trapped with Tad in the sweltering, broken-down car with the monstrous dog waiting outside.