In the late eighties, Dutch artist Hans Citroen meets Barbara Starzyńska, a Polish architect, and ends up visiting relatives in Oświęcim, the city where his grandfather survived KZ Auschwitz.

In and around Oświęcim, Citroen notices many incongruities that do not seem to disturb other visitors. Looking for an explanation, Starzyńska and Citroen speak with archivists and curators and explore the sites many times. Most of their research covers the years that followed the Holocaust. Bit by bit, they find a hidden city.