Benectine monk Brother Cadfael must solve a murder that takes place in a house owned by his abbey.
It is December 1138 in Shrewsbury Abbey, where former sailor Brother Cadfael serves under the lenient Abbot Heribert. But all is about to change, as a consequence of the civil war occurring in England at this time, Heribert has been summoned to a legatine council in London at which his future as abbot will be discussed. His last order of business is allowing Gervase Bonel and his family to move into a house the Abbey owns. They also get food and a few other consideration in return for Gervase gifting his manor to the Abbey.
Heribert heads to London, leaving Prior Robert, who is eager to take Herbert's place, in charge. Brother Cadfael returns to his duty as the Abbey herbalist, he prepares a joint liniment, using the dangerous herb Monk's Hood, for elderly Brother Rhys. When Cadfael visits Rhys he finds the old man has company, his great nephew Meurig. Cadfael also meets the Bonel's servant Aelfric, who mentions that Gervase cut his stepson out of his inheritance in favour of the Abbey.
When the Prior shares his partridge dinner with Gervase he becomes suddenly violently ill. Cadfael and Brother Edmund the infirmarer rush to help but they cannot save him. Cadfael recognises the symptoms as Monk's Hood poisoning and is also stunned to learn that Gervase's wife is an old love of his from before he took holy orders, Richildis.
The Sheriff's sergeant immediately suspects Gervase's 15 year old stepson, Richildis's son, Edwin, especially since the boy seems to have fled. Edwin had visited Rhys with Meurig and so had access to Monk's Hood. Cadfael gets to talk privately to Richildis and learns of her life since their last meeting 40 years ago. He learns that her unusually young son Edwin is also Uncle to her grandson Edwy, who is virtually the same age. The boys are very close and Edwin is apprenticed to Edwy's father, Martin Bellecote, who married Edwin's older sister. Richildis is certain of her son's innocence and begs Cadfael to help. She also tells Cadfael that Meurig is in fact Gervase's illegitimate son, and Aelfric had been a freeman until Gervase made him a villein.
Cadfael lays bait for Edwin and he and Edwy come to the herbarium by night (Edwy initially pretending to be Edwin). Cadfael ascertains Edwin's innocence by letting the boy believe his stepfather was knifed and then hides him in an abbey barn disguised as a monk.
Cadfael visits Richildis to tell her that her son is alright and they talk a little of old times. But he is overheard by Prior Robert's toadying assistant, Brother Jerome, who brings the matter up at Chapter and suggests that Cadfael should be stopped from seeing Richildis again for his own sake. The Prior agrees and Cadfael is confined to the Abbey grounds.
Edwin is discovered by the Sheriff's men and escapes on a stolen horse. But soon reports come in that he has been captured and he asks for Cadfael. When Cadfael sees the boy he is able to tell the Sheriff that this is not Edwin but Edwy. And Edwy is in luck as it is the Sheriff's deputy, and Cadfael's friend, Hugh Beringar who is sent to deal with him, and who releases him on parole.
Cadfael's assistant Brother Mark finds the bottle the poison was kept in discarded in a place where Edwin could not have thrown it, further proving his innocence and telling Cadfael that the bottle leaked.
Cadfael is sent to help a sick lay brother who tends the abbey's sheep near both the Welsh border and the Bonel Manor. Discovering the manor is in Wales, Cadfael now wonders if this is significant; laws are different in Wales. Having helped the lay brother, Cadfael visits the family of elderly brother Rhys to deliver a message, but there he finds Edwin in hiding. Unfortunately Cadfael has been followed by the Sergeant who arrests Edwin.
The next day Cadfael goes to the Commote court (a local Welsh court). There he sees Meurig make his case for ownership of the Bonel manor, under Welsh law the fact that he is illegitimate does not matter. The court is about to find in Meurig's favour when Cadfael accuses him or murder and proves it with the distinctive stain the Monk's Hood liniment has left in Meurig's pouch. Meurig escapes but word will be sent to the Sheriff in Shrewsbury so Edwin can be released.
Cadfael returns to the sick brother but Meurig comes for him. However, Meurig cannot kill him and instead Cadfael hears his confession and, knowing that the boy has been much mistreated and is not a killer by nature, lets him go.
Cadfael returns to the Abbey the same day as Abbot Heribert, who is now no longer Abbot. But Prior Robert will not take over either, Heribert is replaced by Abbot Radulfus. Edwin is now master of the Bonel Manor, Aelfric is freed and Cadfael has the chance for once last conversation with Richildis before she and her son head home.
Best part of story, including ending:
This is a very well-written murder mystery that keeps you guessing but is not impossible to solve yourself.
Best scene in story:
I like the scene of Brother Cadfael talking to his old love Richildis whom he has not seen for 40 years. She is now twice widowed with two children, he is now a monk, it is never going to happen between them but it is a touching scene.
Opinion about the main character:
Cadfael is above all a decent man who tries to help people without breaking his vow to God. He is too old for abbey politics and has found a peaceful life that suits him.