Third in a series from Grace (a.k.a. P.C. Doherty) set in medieval England and featuring Kathryn Swinbrooke, Canterbury's city physician (The Eye of God, 1994, etc.). Working with soldier Colum Murtagh, the King's Commissioner (Kathryn's love but not her lover), she's confronted with a series of knotty puzzles. Most urgent is the poisoning death of the King's tax collector Sir Reginald Erpingham -- a greedy, blackmailing lecher found in a tavern room locked and bolted from the inside; his wineglass containing no poison; his sacks of silver holding only rocks. It soon develops that everyone at the Wicker Man tavern, including the surly proprietor and his wife, had reason to hate the victim. The plot thickens, though, when Erpingham's servile clerk Vavasour is found drowned in a frozen pond nearby, newly minted coins scattered on the floor of his tavern bedroom. Even more stressful to Kathryn is the imprisonment of dying painter Richard Blunt, an old acquaintance, after Blunt's young, flighty wife and two of her admirers are killed. Add to this the disappearance, in a raging snowstorm, of Colum's helper Henry Frenland, and Kathryn's growing fear that her brutal soldier husband, long missing, may some day reappear. Finally, the solutions are a bit overelaborate, and too many peripheral characters, mostly unmemorable, clutter the landscape. But the medieval backdrop has a lively reality, the puzzles are sporadically engaging -- and this time out, Kathryn and Colum are warmer and more appealing. The best of this series so far.