When 12-year-old Leo Finch discovers a glowing letter under his grandmother's floorboards, he's whisked aboard the Starlight Express—a celestial train that rides the Skyway between worlds. With a talking ferret named Noodle and a satchel of urgent cosmic mail, Leo must restore the stolen Orion's Belt before reality unravels. But the Composer, a shadowy entity rewriting existence itself, will stop at nothing to claim Leo's mysterious key. Can a Moonlit Messenger deliver hope to the stars—or will the universe's story end forever?