Manfred Goldberg will never forget the day his brother Herman disappeared. It was 1943 and the two young boys were imprisoned in a Nazi slave labour camp for Jews outside Riga, Latvia. Manfred, 13, was taken to work each day, repairing railway tracks destroyed by Allied bombing. Herman, 9, was one of a small group of younger children permitted to stay in the camp during the day.

“One day we returned from work and the children had gone,” Manfred recalls. A member of the kitchen staff told them that two SS men had come to the camp that day and taken the children away. Herman was never seen again. “It’s practically certain these children were dead before the end of the day,” says Manfred…