July 1284. King Edward has invited the nobility of England, Ireland, and Scotland to Nefyn, one of the most remote spots in Wales, for a Round Table - a tournament as in the tales of King Arthur to celebrate Edward's victory over the Welsh and his ascension to Arthur's throne. Not everyone sees the tournament as a friendly competition, however, and in short order, Rhys and Catrin are called to investigate the death of a knight in the retinue of the Earl of Gloucester.

In the aftermath of Prince Rhun's death, King Owain and King Madog agreed their children should marry as a way to seal the peace between them. Two years later, the wedding date has finally arrived, though relations between the two kingdoms have improved only to the extent that they aren't actually at war. So when an innocent falls victim to a poisoned dish, even Queen Cristina is so desperate for the event to take place that she begs Gareth and Gwen to head off another round of murder - and wedding mayhem - in medieval Wales.

January, 1145. Godfrey Bowyer, the best but least likeable bow maker in Worcester, dies an agonising death by poisoning. Although similarly struck down after the same meal, his wife, Blanche, survives. The number of people who could have administered the poison should mean a very short investigation for the sheriff’s men, Hugh Bradecote, Serjeant Catchpoll and Underserjeant Walkelin, but perhaps someone was pulling the strings, and that widens the net considerably.

The year is 1143, and King Owain seeks to unite his daughter in marriage with an allied king. But when the groom is murdered on the way to his wedding, the bride's brother tasks his two best detectives - Gareth, a knight, and Gwen, the daughter of the court bard - with bringing the killer to justice.

1603. Former ship's surgeon Gabriel Taverner is attempting to re-establish himself as a physician in rural Devon but it's not easy to gain the locals' trust and a series of disturbing incidents convinces him that at least one person does not welcome his presence. Called out to examine a partially decomposed body found beside the river, Gabriel discovers he has a personal connection to the dead man.