Felix is a ten-year-old Jewish orphan who relies on his imagination and love of storytelling to survive the hostile environment of Nazi-occupied Poland. Armed with stories by his favorite author, Richmal Crompton, he tries to shield Zelda from the horrific reality surrounding them. Forced to assume the false identity of a Polish boy named Wilhelm, he struggles to maintain his moral compass and natural altruism while navigating a society that wants him dead.

Zelda is a precocious six-year-old girl whose parents were Nazi sympathizers killed by the Polish Resistance. She harbors intense guilt and anger toward her parents, completely rejecting their ideology and falsely claiming to be Jewish out of loyalty to Felix. Under Genia's care, she adopts the alias Violetta but frequently struggles to hide her outright hatred for the occupying soldiers.

Genia is a young Polish farmer managing her homestead alone while her husband is away on forced labor. Though raised in a culture of widespread antisemitism, her fierce hatred of Nazis and anyone who harms children overrides her initial prejudices. She provides Felix and Zelda with food, shelter, and false identities, constantly risking her own safety to maintain their cover.

Cyryl is the young son of local shop owners who support the occupation. He leads a gang of boys in town and enthusiastically repeats the hateful rhetoric he learns from the adults around him. He quickly becomes suspicious of Felix's background and actively seeks opportunities to expose him to the authorities for personal satisfaction.

Amon is a member of the Hitler Youth stationed at the town's former Jewish orphanage. Despite wearing the uniform, he privately disagrees with the agenda he serves and longs for the war to end. He acts as a translator for the guards but uses his position to occasionally shield civilians, bonding with Felix over their shared appreciation for British literature.

Dov is an orphaned Jewish boy who survived a horrific massacre that claimed his family and peers at the local orphanage. Harboring severe trauma and immense rage, he survives by hiding with a local farmer and sneaking out to hunt. He views the world with profound distrust and single-mindedly seeks ways to retaliate against the occupying soldiers.

Mr. Krol is a local turnip farmer who presents himself to the town as a sympathizer to the occupation to avoid suspicion. Behind this carefully constructed public facade, he actively subverts the authorities by hiding fugitives on his property, taking significant personal risks to supply them with basic necessities.

Gabriek is Genia's husband, a Polish man conscripted to perform forced labor for the war effort. His long absence leaves Genia to manage their farm alone, though he remains a constant presence in her thoughts and heavily influences Felix's comforting stories.

Leopold is Genia's large, friendly farm dog. He provides emotional comfort to the children in hiding and serves as a connection to the former orphans of the town, who used to feed him when they were forced to work on the farm.