When twins Lindy and Kris find a ventriloquist's dummy in a dumpster, Lindy decides to "rescue" it, and she names it Slappy. But Kris is green with envy. It's not fair. Why does Lindy get to have all the fun and all the attention? Kris decides to get a dummy of her own. She'll show Lindy. Then weird things begin to happen. Nasty things. Evil things. It can't be the dummy causing all the trouble, can it?
There's something horrible happening in Fever Swamp. Something really horrible. It started with the 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 is just a regular old dog. And most dogs don't howl at the moon. Or disappear at midnight. Or change into terrifying creatures when the moon is full. Or do they?