Brother Cadfael, herbalist-sleuth at Shrewsbury's Benedictine monastery in the 12th century (The Devil's Novice, etc., etc.), is dismayed by the cold, unforgiving nature of Father Ailnoth, the new parish priest of the Foregate. In fact, Ailnoth's short time in office has made him so feared and hated that there's no mourning when his body is pulled from the mill pond on Christmas morning. Ailnoth had come from Westminster, now restored, along with most of the country, to King Stephen, accompanied by a widowed housekeeper and her young nephew, Ninian, who is apprenticed to Cadfael and soon wins his trust and affection. Ninian's guileless indiscretion soon reveals him as an ardent fighter for Empress Maud, the King's archenemy, now regrouping her forces in Wales, and he finds an ally in beautiful Sanan Bernieres. In hiding from Sheriff Hugh Beingar's halfhearted search and accused by some of Ailnoth's murder, Ninian is then set free to join his Empress by the unexpected result of a trap set by Gadfael and the Sheriff. Rather thin plotting for Peters--otherwise, her usual mix of lively period detail, three-dimensional characters and easy-flowing narrative.