In medieval England, Brother Cadfael, a former soldier turned monk and herbalist, uses his knowledge of herbs and his keen intellect to solve a series of murders in his Benedictine abbey. His investigations take him into the feudal society of the time, exploring the dynamics between the clergy, nobleman, and common people. As he uncovers the truth behind each murder, he must navigate the complexities of the English Civil War and the challenges of maintaining justice and order.