As the Red Army approaches a forest in Poland at the end of the war, they stumble upon a massive complex containing over a thousand structures across 25 sq km. The Germans have fled 5 days earlier, taking or destroying as much documentation and equipment as they can. As the Soviets investigate the tunnels and bunkers, curiously carved and built into the forest landscape, to guarantee absolute secrecy, they realize the terrible materials manufactured in Dag Bromberg. How did the Germans keep this colossal base secret from allied intelligence? And what technology and secrets did the base give up behind the iron curtain after the war?