After Alex loses his grandfather's heirloom pocket watch, strange things happen. He meets an odd old woman, and he learns about a blue moon, where lost things go. This leads to an encounter with the Moon Rats, who take Alex and his dog on their ramshackle spaceship to the blue moon. There, Alex meets some eccentric fellow seekers who have lost both material and abstract things, and together, they make their way across the bizarre landscape. Standing in their way are Urd, a powerful witchlike figure, and her helpers, and Alex must outwit her before he can return home. This novel could have been swallowed up by the surfeit of allegorical symbols. Rupp, like the best sf writers, holds the reader's interest, though, with humor and some well-placed excitement. Thought-provoking but also fun. Category: Books for Middle Readers--Fiction. 2006, Candlewick, $15.99.