It is 1943, and for four years, sixteen-year-old Stefania Podgórska has been working for the Diamant family in their grocery store in Przemsyl, Poland. She has even made a promise to one of their sons, Izio - a betrothal they must keep secret since she is Catholic and the Diamants are Jewish. But everything changes when the German army invades Przemsyl. The Diamants are forced into the ghetto, and Stefania is alone in an occupied city, the only one left to care for her six-year-old sister. And then comes the knock at the door. Max Diamant has jumped from the train headed to a death camp. Stefania and Helena make the extraordinary decision to hide Max, and eventually twelve more Jews. Then they must wait, every day, for the next knock at the door, the one that might mean the end of everything.