She was the grandmother he never knew. Marta Goldstein-Kattenburg. Born in Germany. Married to a Dutchman. Murdered at Sobibor death camp in Nazi-occupied Poland in April 1943. Until now, Canadian documentary maker David Kattenburg has had few tangible memories of his grandmother's life and death. This past summer, David traveled to Sliedrecht to find out how Marta is now to be commemorated.