[sufue]

The Assassin's Riddle is the seventh in the Brother Athelstan series by Paul Doherty. It is free right now at Kindle and Kobo US. I don't think I've ever seen one of Doherty's titles go free, although in the past, there have sometimes been big sales of his books at $0.99/$1.99/£0.99/£1.99 price points. Anyway, here's info:

Kindle US: https://www.amazon.com/dp/B0844P8J1K
Kindle US/Smile: https://smile.amazon.com/dp/B0844P8J1K
Kobo US: https://www.kobo.com/us/en/ebook/the...sin-s-riddle-2

Spoiler:

The only way to win this murderer’s deadly game… is to play along.

Summer, 1380. Brutal and sudden death is not uncommon in the foul alleys and streets of London. The corpse of a clerk has been pulled from the Thames. They drowned, but not before receiving a vicious blow to the back of the head.

Then Bartholomew Drayton, a usurer and money-lender, is found dead in his strongroom, a crossbow bolt firmly embedded in his chest: a real mystery because the windowless strongroom was locked and barred from the inside. So who killed him? And how? And are the deaths connected?

Sir John Cranston comes to survey the scene. When other clerks are murdered, each with a riddle pinned to his corpse, Cranston enlists the help of Brother Athelstan – and together they must pit their wits against a deadly adversary bent on murder and mayhem.