The Half-a-Moon Inn by Paul Fleischman

Aaron has never left alone before. He is mute, and depends on his mother for everything. But tomorrow Aaron will be twelve years old, old enough to stay home by himself while his mother goes to town. Everything will be fine, as long as he stays close to the house. And if there's trouble, Aaron can write what he needs to say.

Trouble there is aplenty. When a terrible blizzard keeps his mother from returning home, Aaron sets out to search for her—but he stumbles upon the mysterious Half-a-Moon Inn, where the crafty Miss Grackle forces him to work for her. How can Aaron stop her from carrying out her devilish schemes—before it's too late?