In the Summer of 1940 an underground operative called Witold Pilecki accepted a mission to uncover the fate of thousands of people being interred at a new concentration camp on the border of the Reich. The name of the detention centre -- Auschwitz. Over the next two and half years, Witold forged an underground army that smuggled evidence of Nazi atrocities out of Auschwitz. His reports from the camp were to shape the Allies response to the Holocaust - yet his story was all but forgotten for decades. The true story of the resistance hero who infiltrated Auschwitz.