The Assasin's Curse by Kevin Sands

This is the third in the Blackthorn Key series.  In this one Christopher and Tom are called to meet the King of England who wishes to thank them for their service stopping the plague doctor (in the previous book).  While they are at the palace, an attempt is made on the life of the king and his sister, the lady Minette.  The king enlists Christopher, Tom and Sally to accompany Lady Minette back to her home in France and try to discover and stop the assassins. In there search they discover a plot related to the old legends of the Knights Templar treasure.

I really like this series.  The first one was a little too violent, but the later ones were better and I really enjoy the characters and setting of this medieval mystery series. Sand's description of the Cemetery of the Holy Innocents was so bizarre that I had to look it up. His descriptions are correct; it really was one great stinking open mass grave. I have come to trust Sand's historical detail. This book ends with the door wide open for more, so huzzah! (532 p. 2017)