More than six million people were killed as part of the Nazi genocide called the Holocaust. More than one million of those people died in two neighboring concentration camps in Poland - Auschwitz and Birkenau. After the Nazis abandoned the camps in December 1944, Russian troops freed the remaining prisoners, destroyed the buildings, and secretly took most of the records from the camps back to Moscow.

In the aftermath of the war, survivors told horrifying stories of gas chambers, mass graves, and huge crematoriums. Many Nazi leaders were convicted of serious war crimes on the basis of these testimonies. However, without specific records such as blueprints and written orders, investigators had some difficulty determining the extent of Hitler's plans for mass extermination. Some Nazi leaders argued that the camps were used only as labor camps and that the crematoriums were used merely to burn the bodies of prisoners who had died of disease or from the harsh conditions. Nearly 50 years later, NOVA joins a British historian who has gained access to the files and gathered powerful evidence to show how Nazi death camps were planned and constructed.