Cujo by Stephen King
Outside a peaceful town in central Maine, a monster is waiting. Cujo is a two-hundred-pound Saint Bernard, the best friend Brett Camber has ever had. One day, Cujo chases a rabbit into a cave inhabited by sick bats and emerges as something new altogether.
Meanwhile, Vic and Donna Trenton, and their young son Tad, move to Maine. They are seeking peace and quiet, but life in this small town is not what it seems. As Tad tries to fend off the terror that comes to him at night from his bedroom closet, and as Vic and Donna face their own nightmare of a marriage on the rocks, there is no way they can know that a monster, infinitely sinister, waits in the daylight.