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.

Nearly a century later, in the spring of 2020, Pope Francis announces that he intends to open the Vatican Secret Archives to the public. 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 the 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 one more conducive to the party's own political views and ambitions.