She was a Roman Catholic social worker who, by the time she was arrested by the Gestapo, had managed to smuggle 2500 babies and children out of the Warsaw ghetto, and have them rehomed under fake Christian identities. She kept secret records of their real Jewish names and families to enable them all to be reunited after the war.
She was 98 when she died, and still largely unknown, although she was nominated last year for the Nobel Peace Prize. The obituary I read quotes her as saying:
I was brought up to believe that a person must be rescued when drowning, regardless of religion and nationality.The term 'heroine' irritates me greatly. The opposite is true. I continue to have pangs of conscience that I did so little.