Gervase Bonel is a guest of Shrewsbury Abbey when he is suddenly taken ill.  Brother Cadfael , the Abbey’s skilled herbalist, hurries to the man’s bedside to find two surprises…Master Bonel’s wife is Richildis, whom Cadfael loved before he took his vows; and Master Bonel has been fatally poisoned by monk’s-hood oil from Cadfael’s stores. The sheriff is convinced that the murderer is Richildis’ son, Edwin, who hated his stepfather. But Cadfael, guided in part by his concern for a woman to whom he was once betrothed, is certain of her son’s innocence. Using his knowledge of both herbs and the human heart, Cadfael deciphers a deadly recipe for murder.