In 14th-century Italy, Mondino is a university anatomist - a man of science in a land governed by the brutal Inquisition. But the corpse brought to Mondino's laboratory one stormy night defies natural law: The victim is a Templar knight, and his heart has been transformed into a block of iron.
Is it alchemy? Or the diabolical work of an ingenious killer? Aided by his headstrong student Gerardo - a young man concealing a deadly secret identity - Mondino must outwit both ruthless Inquisitors and vengeful Templars if he's to stop a murderer who threatens to shake the very foundations of Christendom.