Goosebumps : How to Kill a Monster

Gretchen and her sterother, Clark, hate staying at their grandparents' house. Grandpa Eddie is totally deaf and Grandma Rose is obsessed with baking. Plus they live right in the middle of a dark-muddy swamp. Things couldn't get any worse, right? Wrong because there's something really weird about Grandma and Grandpa's house. Something odd about that room upstairs. The one that's locked. The one with the strange noises coming from it. Strange growling noises.