Irena Sendler’s father was the only doctor who would treat impoverished Jewish patients suffering from typhus in a Warsaw epidemic. He contracted the disease, too, but before he died he told seven-year-old Irena that “if she ever saw someone drowning, she must jump in and try to save that person, even if she could not swim.” Irena took those words to heart. As an adult, she smuggled supplies into the Warsaw Ghetto for two years before becoming head of the children’s department of Zegota, a secret organization that helped persecuted Jews in Poland escape during World War II. In 1943 Irena was arrested by the German Gestapo and refused to reveal the names of those she helped, or of others who assisted her efforts, despite torture. Sentenced to death, Irena was freed after Zegota officials paid a bribe. In hiding and with an assumed identity, she continued her resistance work throughout the war. Irena buried lists of the children she helped smuggle out of the ghetto—recording both their real and new, false identities—in glass jars. There were over 2,500 names on the lists by the time the war ended. An afterword tells of the recognition Irena received for her brave deeds, including a nomination for the Nobel Peace Prize in 2007. (Ages 7–11)