In an alternate history in which the Plantagenets still rule in England, France, and the New World, and where the science of magic has displaced the magic of science, Lord Darcy is the official representative of King John IV to investigate murders and other bizarre crimes, and Master Sean O Lochlainn his forensic magician sidekick.

An Azteque prince is sacrificed at the top of an abandoned Azteque pyramid in New England, his heart torn from his chest in a fashion discarded hundreds of years earlier. Unless Darcy and Sean can uncover the how and why of the crime, the fragile peace between the Angevin settlers of New England and the Azteque Empire may soon be broken.

Another first-class authorized continuation of the magical detective series begun by the late Randall Garrett.