Grandpa Will gets very upset when discussing the war or seeing Nazi soldiers on television because his experience as a prisoner in the concentration camp during World War II was as horrific as can be imagined. At the camp, Grandpa, who was only a teenager at that time, was assigned the job of carrying the body of dead Jews to the ovens to be burned. His task was so traumatic that he became a musselman, someone who decides "that life is not worth fighting for," and just goes through the motions of living each day in a haze. Grandpa Will, who was called by his real name "Wolfe" in camp, did survive his ordeal, but the experience left his mind forever unstable. He does manage to live a fairly normal life after the war, marrying and having a child, but he is subject to periodic rages which are triggered by images which remind him about what happened in the camp.
When Hannah and her family arrive at Grandpa Will's house to celebrate Passover, Grandpa Will is watching television,
"waving his fist and screaming at the screen. Across the screen (march) old photos of Nazi concentrations camp victims, corpses stacked like cordwood, and dead-eyed survivors."
As the horrible images flash by, Grandpa sits shouting incoherently at the TV, holding up his left arm to show the tattoo that is forever etched there, the five-digit number which identified him as a prisoner in the camp. Aunt Eva apologizes for her brother Will, and the adults present seem to understand Grandpa acts the way he does. Hannah, however, does not know the full impact of what went on during the war, and is a little annoyed. It is only after she herself is mysteriously transported back in time to the camp that Hannah realizes the full implications of the atrocities that were visited upon the Jews and other victims of Hitler's regime during that infamous time.