Ruth Elias was 17 when the Nazis occupied Czechoslovakia in March 1939. After three years of hiding on a farm, the family was denounced and deported in to the Theresienstadt camp in April 1942. During the winter of 1943, Ruth found out she was pregnant – she then learned that she would be part of a convoy to Auschwitz. During a selection in June 1944 – when she was 8 months pregnant – she managed to be part of 1000 women sent to clear rubble at a refinery that had been bombed in Hamburg.

Ada Lichtman was faced with absolute horror from the start: the day the Germans invaded Poland, all the men in Wieliczka – a little town near Kracow where she lived – were rounded up by the Germans, driven to a nearby forest and executed. Ada Lichthman explains how, after being transported to Sobibór, one of her tasks included washing and dressing dolls stolen from Jewish children on the transport that could then be passed on to Nazi officers. It’s a small anecdote among many, but one that succinctly locates the trauma of reliving the bizarre meld of cruelty and irrationality that these [Four Sisters] films examine with unshowy virtuosity.

There are still archives, diaries and even some photos of the Lodz ghetto, but very few actual witness accounts from survivors. Paula Biren's is all the more exceptional, with her having been part of the ghetto's Jewish women police at the time. Her sharp eye for detail as well as her dazzling intelligence underscores her incredible testimony. Of the hundred ghettos that dotted the Polish countryside, the one in Lodz had existed for the longest. It was ruled with an iron fist by the president of the Jewish council of elders, Chaim Mordechai Rumkowski, known as "King Chaim" – a man convinced he could save part of the community by turning them into manpower to serve the Germans.

In 1944, when the Nazis started deporting Jews from Hungary, Rudolf Kastner – a Zionist leader of the Aide and Rescue Committee – negotiated with Adolf Eichmann to secure a train boarded by 1684 Jews to leave for a neutral country in exchange for payment. Hanna Marton was one of the passengers. Hanna Marton is from Cluj (now Romania), formerly the capital of Transylvania. Both Hanna Marton and her husband were lawyers and Zionists. Marton was aboard the train organized by Rudolf (Rezso) Kasztner, carrying 1684 'privileged' Jews that left Hungary for Germany, eventually bringing them to Bergen-Belsen on 9 July 1944. Claude Lanzmann asks questions in French, which Hanna Marton understands, although she replies in Hebrew.