Wings of Fire

In Charles Todd's Wings of Fire, Inspector Ian Rutledge is quickly sent to investigate the sudden deaths of three members of the same eminent Cornwall family, but the World War I veteran soon realizes that nothing about this case is routine.
Including the identity of one of the dead, a reclusive spinster unmasked as O. A. Manning, whose war poetry helped Rutledge retain his grasp on sanity in the trenches of France. Guided by the voice of Hamish, the Scot he unwillingly executed on the battlefield, Rutledge is driven to uncover the haunting truths of murder and madness rooted in a family crypt...