Alex Werber calmly strode toward a patch of black stones, pulled up his sleeves and opened a plastic bag to dump out its contents. “Goodbye, mom,” he said, scattering her ashes at the former site of the Treblinka death camp in Poland, where the Nazis murdered 875 000 Jews during World War II. It was Lucy Werber’s final wish: To have her body cremated, her ashes taken to Poland and sprinkled at the death camp that killed her entire family, a fate she narrowly avoided when she was a young girl.