The invasion of Poland by Nazi Germany marks the beginning of World War II and the start of hardships for Polish Jews and resistance members like Irena.
The Warsaw Ghetto is established by Nazi Germany to confine the Jewish population of Warsaw, later becoming the site of deportations to concentration camps.
Irena Sendler, working with the Polish Underground, begins smuggling Jewish children out of the Warsaw Ghetto, saving them from the Holocaust.
Irena is arrested, tortured, and sentenced to death for her activities helping Jewish children escape the ghetto, but she manages to avoid execution.
Jewish inhabitants of the Warsaw Ghetto rise against Nazi forces in a significant act of resistance, though eventually suppressed.