The silver sword links the children (Ruth, Edek, and Bronia) to their father and symbolizes hope.
The first mention of the silver sword is in chapter four. Their father, Joseph, returns to Warsaw after escaping a Nazi prison camp. He finds his house destroyed and family missing, but he locates the silver sword in the rubble. He gives the sword to a young boy, Jan, and asks Jan to help him find his family.
In chapter eight, Jan is sick and Ruth brings him in to their hide-away in the bombed out cellar. When the children find the silver sword among Jan's possessions, they know that their father is looking for them. Jan tells them to go to Switzerland to find their parents.
In chapter 21, the children are hiding in a farm house with Kurt Wolff. The Burgomaster comes to tell Kurt that all children must be returned to Poland. Kurt uses the silver sword to try to prove to the Burgomaster that the children will be reunited with their family in Switzerland. The Burgomaster is unimpressed, however, and the children have to escape in Kurt's sons' canoes.
In Chapter 24, the silver sword goes missing and the children worry that it is a sign that their parents will remain missing. However, luck is on their side and they meet up with an American of Polish descent who helps them by taking them to a Red Cross camp near the border to Switzerland.
At the camp, they receive a message from their father, and the silver sword is returned to them via a message from Kurt.
The last time the sword has significance is in chapter 28, when the children are reunited with their parents after a perilous storm and a rescue by boat. Jan tells Margrit (the children's mother) that he held on to the silver sword and asks to be adopted into their family. At this point, the silver sword symbolizes Jan's hope to have a family. He held on to the silver sword just like he held on to his desire to be part of a family.