Jacob is one of the Jewish children that Barney is hiding from the Nazis. Because he blinks so much, Felix sometimes calls him “the blinking boy.” He figures out a method of piling mattresses so that the children hiding in the cellar can see through a high crack into the street. Zelda becomes convinced she’s seen her mother through the crack, an incident that finally convinces Felix to admit to her that he saw her parents’ corpses. Later, Jacob tells the other children that Nazis burnt his entire family to death.