It's Halloween, and Mitchell's littlest sister, Gretchen, looks up at the moon and sees that part of it is missing. Gretchens other siblings, Annabelle and Clark, scornfully tell her that the moon is just hiding behind some clouds, but Mitchell indulges her and sets out to save the moon. A humorous and slightly scary fantasy ensues before the four children set off for trick-or-treating. This spooky fall story joins Clark in the Deep Sea, Gretchen Over the Beach, and Annabelle at the South Pole in a four-book series that celebrates the power of imagination, created by the veteran children's book illustrator R. W. Alley.