Part 3 opens one year after the closing events of Part 2. It is now July 1944. The Nazis are leaving Warsaw, after receiving news that Soviet Union forces are on their way to liberate the city. Nazi soldiers pack trucks with books stolen from the library warehouse—books that the Nazis are claiming for themselves and taking out of Poland. The Fraus, not yet retreating with the rest of the government officials, accuse Zofia of stealing from the Reich by hiding books that were supposed to be destroyed. Zofia claims innocence and tells the Fraus to search her desk. There, disguised as a box of chocolates, Zofia has hidden a bomb. The Fraus take the supposed chocolates and open the box in their car. The resulting explosion kills them both.

The library staff, now under the direction of the Polish Mr. Bykowski, prepare the library for the coming battle. They fortify the building, planning to keep both books and people safe when fighting erupts. The Polish Home Army launches their attack against the German General Government on the evening of August 1. Zofia and Janina prepare by moving Matka and Miss Laska to the relative safety of the library.