The time for deception is over. Jan Kalisz must choose: fight for his country's freedom, or save his family. June 1944. When a Wehrmacht war crimes investigator and his escort are killed in an ambush, it looks like an opportunistic act of revenge by the Polish Resistance. But Jan Kalisz of the Warsaw Kripo, investigator and Polish double-agent, has his doubts. Fortunately, with the Red Army only a few hundred kilometres from the city, Kalisz's boss, Hauptsturmführer Hoth, finds his faith in the Führer waning, and allows an investigation. The hunt for the real killers takes Kalisz first to a war-torn Berlin and then within reach of Soviet artillery, but to uncover the truth he must enter the very gates of Hell. And waiting for him at Auschwitz-Birkenau is his former associate, Doctor Josef Mengele, the Angel of Death… Warsaw is a powder keg on the brink of exploding. After five years walking the knife edge between deception and collaboration, is it finally time for Jan Kalisz to reveal his true allegiance? The explosive finale to the acclaimed Warsaw Quartet series.