Felix is a thirteen-year-old Jewish boy who has spent two years hiding from the Nazis on a rural Polish farm. He relies heavily on his vivid imagination and his favorite adventure books to cope with his frightening reality and isolation. Forced to abandon his hiding place, he rapidly adapts to the brutal conditions of the war, learning to survive in the forest and ruined towns. Despite the violence around him, he maintains a strong desire to mend rather than kill.

Gabriek is a Polish farmer who risks his life to shelter Felix from the occupying German forces. He acts as a surrogate father to the boy, providing him with physical sustenance and reading material to keep his mind sharp. While maintaining the appearance of a cooperative cabbage farmer, he secretly works to sabotage Nazi infrastructure alongside the Polish resistance.

Yuli is a fierce young Russian partisan who fled to Poland and joined the resistance after her parents were killed in a German work camp. Bearing physical scars from past battles, she demonstrates ruthless efficiency when engaging enemy soldiers in combat. Within the partisan camp, she takes on a protective role toward Felix, teaching him practical survival skills and attempting to shield him from emotional despair.

Szulk is a tall, hostile fighter within the Polish partisan group. He harbors intense antisemitic prejudices and openly despises Felix for being Jewish. He constantly voices his desire to execute the boy, viewing him as an unnecessary liability who will attract German forces to their hidden camp.

Dom is a massive, compliant farm horse belonging to Gabriek. Having lived just inches above Felix's hiding spot for two years, the horse becomes an essential companion once the boy emerges. Dom provides vital transportation and physical strength for tasks Felix cannot manage alone.

Dr. Zajak serves as the primary medical provider for the Polish partisan forces living in the forest. He operates in squalid, poorly lit conditions using heavily restricted supplies. Recognizing Felix's steady hands and empathy, he recruits the boy to assist him with gruesome field surgeries.

Pavel is the authoritative leader of the partisan resistance group operating in the forest. He enforces strict rules to maintain the secrecy and safety of their camp, demanding absolute obedience from his fighters.

Axel is an orphaned German boy wearing a Hitler Youth uniform who survives in the rubble of a heavily bombed town. He aggressively guards a hoard of stolen canned food, struggling to feed himself and his young companions.

Helmut is a young German boy who initially appears as an intimidating figure in his Hitler Youth uniform. When encountered later in the ruined town, he is revealed to be a desperate, hungry orphan trying to protect his little sister.

Bug is a young, blonde-haired German girl orphaned by the war. She relies entirely on her older brother and his friend for protection and sustenance in the ruins of their town.

Hannah is one of three young Jewish sisters hiding in the wreckage of a bombed town. Following the death of the woman protecting them, she faces severe starvation until Felix discovers their location.

Beryl is a young Jewish orphan struggling to survive the occupation. Like her sisters, she must overcome her fear and learn to share resources when Felix leads them out of the town.

Faiga is the third of the Jewish orphan sisters. Thrust into close quarters with German children on an isolated swamp island, she participates in the daily squabbles typical of young people forced to share limited supplies.

Mr. Rosenfeld is a surviving prisoner from Felix's hometown who has endured the horrors of the concentration camps. Weakened significantly by starvation and disease, he provides Felix with critical information regarding his parents' whereabouts.

Felix's mother was a bookseller before the war systematically destroyed her family's life. Having been transported to a massive death camp, she suffers deeply from severe illness and the physical toll of her prolonged imprisonment.

Felix's father operated a bookstore alongside his wife before being captured by the occupying forces. He remains a powerful presence in Felix's thoughts and fantasies as the boy desperately searches for his family.