At the Bendictine monastery in Shrewsbury in 1138, the gardens are flourishing under the expert tending of Brother Cadfael. His shelves boast all sorts of medication for every kind of ailment. But then a local landowner is poisoned with Cadfael's own concoction intended for aching joints.
As the monk investigates he finds a web of family intrigue, where suspicion has fallen on someone he is certain is innocent.