Max is an eleven-year-old Jewish boy living in the harsh conditions of the Esties ghetto in Poland. After his mother's death and his father's recent arrest by the Nazis, Max assumes the responsibility of caring for his younger sister. He feels angry about the destruction of his town and the prejudice of former neighbors, driving his determination to protect his only remaining family.

Zena is Max's nine-year-old sister. She has a delicate, doll-like appearance with blonde curls and round cheeks that hides her inner toughness. Despite the grim reality of the ghetto and the constant threat of starvation, Zena actively looks for signs of good luck and maintains a surprisingly positive outlook.

Hannah is Max and Zena's nineteen-year-old aunt. Before the occupation, she was known in Esties as a wild, bookish teenager saving money to move to America. The war has hardened her into a tough, practical resistance fighter who wears men's clothing and plots sabotage missions against the Nazi army.

Referred to as Papa by his children, Max's Father owned an electrical repair shop in Esties before the Nazis destroyed it. The Nazis arrested him a month before the main events of the story, leaving his children to survive alone. He serves as an emotional anchor for Max through memories of his advice regarding prejudice and survival.

Mr. Jablonski is a Polish farmer with roughened hands and a sunbaked face. While he maintains a friendly relationship with the local Nazi commander to avoid suspicion, he secretly works as a spy and safe harbor for the Jewish partisans, risking immediate execution to hide people in his barn.

Lev is the leader of Aunt Hannah's partisan group. He is small and muscular with round glasses that give him a bookish, intellectual appearance. Despite his quiet look, he orchestrates dangerous sabotage missions against German supply trains and serves as a steady, strategic mind for the resistance.

At seventeen, Martin is the youngest fighter in Lev's partisan group. He is a large young man with a quick laugh who uses humor to defuse tension among the exhausted resistance members. In combat, he proves to be a decisive and protective fighter.

Dr. Zelman is a former surgeon who now lives in the hidden partisan camp in the Loda Forest. He uses his medical expertise to treat injured fighters and refugees who manage to reach the island sanctuary.