Face at the Window

Aleksander is sure he's glimpsed a face at the window, high up in the old print works, but everyone knows that is empty. Then he hears that Jews are hiding! He then discovers that his teacher is their helper. He becomes Hannah's penpal but gets increasingly worried about her. Either the bombs or the Gestapo will kill her. Is it true that there's a man called 'Bielski' who is hiding Jews in the forest? There's only one way to find out, but will he even survive such a perilous undertaking in a forest full of hungry wolves and black bears?