Goosebumps- The werewolf of fever swamp

There's something horrible happening in Fever Swamp, something really horrible. It started with strange howling at night. Then there was the rabbit torn to shreds. Everyone thinks Grady's new dog is responsible. After all, he looks just like a wolf and he seems a little on the wild side, but Grady knows his dog and most dogs don't howl at the moon or disappear at midnight or turn into terrifying creatures when the moon is full or do they?