1943. Garda Inspector Stefan Gillespie, on a diplomatic mission for the Irish government, takes a train from the chaos of German-occupied Rome to the Reich itself. Late at night he waits for a long-delayed connection at an empty station in neutral Switzerland.

He sees a train no one is meant to see. A train that shouldn't be there. A beating from the train's SS guards, who shouldn't be there either, leaves him badly injured.

Recovering at an Irish diplomat's home, the story of Stefan's journey to Rome reveals something else that was never meant to be known. The brutal murder of an idealistic young priest in a defeated city, and the dark underbelly of espionage, deception and betrayal that the corruption of war has injected into the City of God itself... the Vatican.