What is the climax of chapters 17-20?
Sometimes, reading over helps. What is important is the contrast between Jan and Edek. In Chapter 17 and again in Chapter 20, we are reminded of how "street smart" Jan is. When Edek discovers that Jan is up to something, he insists on an explanation. Despite Jan's warnings telling Edek to leave, Edek places himself in the open and is caught by an American soldier. In Chapter 20, Edek is naive in thinking that his use of German was so good that they were clear of danger after their encounter with the stranger who had suffered a blown tire. When Edek says at the end of that chapter, "Anyway, I think we got away with it", Jan's response is, "That's what you think". This shows that Jan is always alert and never drops his guard. He is trusting of no one and has good instincts which aid in their survival. The war may have ended but the children are certainly not free of danger. Their target is to get to Switzerland to find their parents and Jan and the silver sword are symbolically, their key. These chapters also prepare us for a turn of events. For a while the children were no longer on their own, but by the end of chapter 20, their cover is exposed and they have to leave the farm. Jan's meeting with Ludwig is also important as Jan will have to make the most difficult decision of his life. We learned of how attached Jan is to his pets and pretty soon, Jan will have to sacrifice Ludwig to save Ruth and Edek.