Why was Ruth too tired to do anything as they drove in the truck to Switzerland

Chapter 25:

As the truck rattles down the road, Ruth tells Joe about their quest, but privately worries more and more about Edek. Joe explains that he is with the Occupation. He was sent to Germany even though he couldn’t speak German, and his job was to rally people in favor of the occupation. Most of the time, though, people are too weary and melancholy to care.

Joe’s driving is a bit precarious, and it also becomes apparent there is something in the back of the truck; he tells the children there is nothing there but a couple of wild animals. When Bronia smiles that Jan would like that, Joe asks her who Jan is. They tell him, and Joe replies that he once knew a boy like Jan.

A bark sounds from the back, and Joe teasingly asks if they’d like to see the hyena. They pull over and, to their surprise, he reveals Ludwig and Jan. Jan is tied up so he will not escape, and he remains that way for the rest of the miles to the Red Cross camp at Lake Constance.

Across the water are the gloriously green hills of Switzerland and the majestic Alps behind them. Ruth gasps; she has never seen anything so incredible. She asks if Jan can come out, and Joe complies. Jan has no more fight in him, and when he sees the mountains he bursts into tears.