Cujo is a massive St. Bernard and beloved family pet living with the Cambers in Castle Rock, Maine. After chasing a rabbit into a cave, he is bitten by a rabid bat. As the disease takes hold, the gentle dog begins transforming into a dangerous and unpredictable animal.
Meanwhile, Donna Trenton is dealing with problems in her marriage and an unreliable car. When she takes her young son Tad with her to the Cambers’ rural garage for repairs, they arrive to find Cujo waiting.
Trapped inside their broken-down car during the summer heat, Donna and Tad have nowhere to go. With no one nearby to help and Cujo preventing them from leaving, their ordinary trip to a mechanic becomes a desperate fight for survival.
Cujo builds its horror around a frighteningly plausible situation, bringing together a family’s personal struggles, isolation, bad timing, and a beloved animal transformed by disease.