The Silver Sword offers a realistic portrayal of the challenges of war through the perspective of a Polish family shattered by World War II. The main characters are three siblings—Ruth, Edek, and Bronia Balicki—who are forced to fend for themselves on the streets of Warsaw after their father is sent to a prison camp and their mother is taken to Germany for forced labor. Serraillier delves into themes of courage, selflessness, loyalty, and honesty as the children strive to survive in a world ravaged by conflict.

Although violence is not depicted graphically, a significant portion of the novel unfolds immediately after the war. The children's hardships stem from the widespread deprivations inflicted by war on their society. Overcoming the hatred bred by the war is crucial for creating a society where people from formerly hostile nations can coexist peacefully.

Serraillier emphasizes that peaceful societies must be built on love and trust, illustrating this theme most clearly through the relationship between Ruth, who exemplifies "courage, self-sacrifice, and greatness of heart," and Jan, an orphan who has learned to survive by stealing. Ruth's affection gradually transforms Jan from a state of selfishness to one of loyalty and self-sacrifice. The Silver Sword is a tale of hope and love, as the children embark on a journey to find their parents, revealing their essential qualities along the way.