The Admirable Physician - The Gareth & Gwen Medieval Mysteries, #16

Gareth and Gwen investigate murder amongst the Hospitallers in The Admirable Physician, the sixteenth Gareth & Gwen Medieval Mystery! April 1150. War has come yet again to Ceredigion, and Prince Hywel marches south alongside his wily uncle, preparing to battle his own cousins. Meanwhile, Gareth and Gwen learn of murder and treachery among the Hospitallers, who are succoring the ill and wounded within the army.
As they investigate, even in the midst of war, they uncover not only murder, but treason and betrayal as well-and inadvertently set the stage for that long-awaited final reckoning within King Owain's court. Complete Series reading order: The Good Knight, The Uninvited Guest, The Fourth Horseman, The Fallen Princess, The Unlikely Spy, The Lost Brother, The Renegade Merchant, The Unexpected Ally, The Worthy Soldier, The Favored Son, The Viking Prince, The Irish Bride, The Prince's Man, The Faithless Fool, The Honorable Traitor, The Admirable Physician.
Also The Bard's Daughter (prequel novella).