Sorrow and a magnificent bleakness suffuse this excellent addition to the saga begun with The Wolves of Willoughby Chase. On his deathbed, England's widowed, games-loving King Richard is in hiding, tended by an elderly cousin and Simon, duke of Battersea. Because Richard has no surviving children, there are many with competing claims to England's crown. Among these are the werewolf Baron Magnus Rudh, and his son, the despicable Lot, who kidnap Simon's good friend, the mettlesome Dido Twite, hoping she can lead them to the king. Meanwhile, Rudh's estranged daughter, Jorinda—a first-class flibbertigibbet—has set her cap for Simon. Even more so than in earlier novels, Aiken's villains mean business: The author underscores the dangers of Dido's plight with scenes of utterly chilling cruelty—first one character (physically depleted from having been imprisoned in a small box for an unknown length of time) is casually tossed into a moat filled with man-eating fish, and then, just a few scenes later, another character is gunned down as he attempts to cross the moat on stilts. Playful, urgent and wildly inventive, Aiken's language is always potent. Readers with a taste for mystery and complexity will find much to savor. Ages 10-up. (June)