April 1945: Europe is in ruins, and Berlin is burning. As the Red Army closes in on the last few blocks surrounding the Fuhrerbunker, a famous aviatrix lands her light aircraft in the center of the shattered German capital. Two days later she takes off again. With her is a man called Heinrich Bechmann, SS mass killer and personal bodyguard of the German chancellor Adolf Hitler—and with Bechmann is a file of documents.

Fast-forward to the fall of 2018, when Pope Francis announces that he intends to open the Vatican Secret Archives to researchers and historians investigating relations between his predecessor, Pope Pius XII, and the Nazi regime. A week later, masked gunmen kill five people at an isolated Jesuit retreat in the mountains of Sicily. And two weeks after that, the body of a celebrated British historian is discovered in a beach house on Long Island. Aiden Blake, ex–Royal Marine and brother of the dead historian, believes there is a mysterious link between these events, stretching across seventy-five years of history.

He’s right—and history itself will provide the clues. The trail will lead him and his brother’s New York–based researcher, Hannah Harper, across the Atlantic to the hidden bunkers of Berlin, a Gothic castle in South Tyrol, Rome, Sicily, and deep into the past in a bid to find his brother’s killers—and expose a neo-Fascist plot to kill the present pope and replace him with someone more conducive to the party’s own political views and ambitions.