After quarreling with his good friend Katy, Rupert is wakened by a fearsome ""Grabbly""; Katy hears their straggle, rushes to the rescue, and is carried off instead--thus initiating Rupert's book-long journey to rescue her. Along the way, he falls in, first, with friendly pirates whose ship is wafted through the air by children's pleasant dreams and later with a gruff old badger. Reaching Castle Dread, the travelers find it full of captive children--including Katy--working at computers: the resident wizard plans to transform all good dreams into nightmares. Rupert bravely leads the children to safety, foiling the wizard with rockets, having been warned earlier that creatures of darkness must be countered by light. They get home, of course, at dawn. There is an appropriately dreamlike quality in the way Rupert mysteriously knows things (like needing Katy's lost slipper in order to rescue her) and is suddenly, inexplicably, empowered for the rescue, but there's no real suspense, in spite of some clever dialogue and engaging action. The Grabblies, who prove to be good dreams transformed (e.g., a nice alligator in a bedtime story turned nasty in a dream), are a clever invention. Pleasant, accessible fantasy, but not outstanding.