In April 1920, a body is discovered in the ruins of Fountains Abbey wearing a cloak and gas mask, with a book on alchemy nearby. The theatrical arrangement conceals the victim’s identity and directs suspicion towards a remote settlement created around a mysterious white horse carved into the landscape. Rutledge follows connections between scientific research, wartime service and a community that resents official intrusion.
The gas mask makes the dead man an image of the recent war, while the abbey ruins and alchemical symbols pull the case into an older vocabulary of secrecy. The mystery considers the moral consequences of wartime science and the ease with which fear of dangerous knowledge can be manipulated after the Armistice.