King of Hearts is based on the true story of the life of Izolda Regenberg a young Jewish woman trapped in the Warsaw ghetto with her husband and their families during the Second World War (the historical Izolda Regenberg was very close to Krall to whom she told her life story. Izolda died in Israel in 2009).
King of Hearts tells how Izolda escapes from the ghetto and lives disguised as an Aryan Polish woman named Maria Pawlicka. Her all consuming obsession is to save her husband and is the impetus for the play. She returns to the ghetto to try and free her parents and her husband. But he is deported to the death camps. The action follows Izolda's efforts to free him by any means.