Meet the Mudsters—a mischievous group of friends and foes who keep the Treetures on their toes. The Mudsters are decomposers. If a decomposer lands on a healthy tree, he can harm it. When the Mudsters notice a hole in a young apple tree, they distract the Treetures by throwing a party so they can sneak into the tree. Will the Treetures stop them from destroying the tree before it’s too late?