Dragon's Lair — Sharon Kay Penman

July 1193: Richard Lionheart, eldest and most favored son of Dowager Queen Eleanor, languishes in a German dungeon, held for ransom by the Holy Roman Emperor. In England, his brother John, desperate for the crown, plots with the King of France to make sure Richard never leaves his prison alive. But the Queen has already begun to meet the ransom demands. It is only a matter of time before the Emperor turns over his royal prisoner.

And then one of the ransom payments vanishes in the fastnesses of Wales, itself wracked by rebellion and intrigue. Into this maelstrom, Eleanor sends her trusted man, Justin de Quincy. Murder soon follows.