Joris is a ten-year-old boy living with his family in a windmill called the Watchman during the German occupation of Holland. He possesses a strong sense of justice and innate compassion, immediately springing into action when he sees others in trouble. Despite his youth and the frightening realities of the occupation, he actively looks for ways to help people.

Dirk Jan is fourteen years old and old enough to remember what life was like before the war began. He shares his family's patriotic values and actively seeks ways to contribute to the Dutch Underground. He is responsible, brave, and resourceful, successfully functioning as a covert courier without drawing the suspicion of occupying soldiers.

Leendert is the eldest son of the Schenderhans family who chooses to collaborate with the occupying German forces as a landwatcher. He enjoys the authority his position brings and readily uses it to intimidate his family and neighbors. He actively searches for fugitives and hidden resources to report back to his superiors.

Mr. Verhagen operates the Watchman, a traditional windmill that drains excess water from the local polder. He worries that new electric mills will eventually render his trade obsolete, though his traditional mill proves essential during energy shortages. He judges people by their practical actions rather than their public appearances and firmly supports the resistance.

Mrs. Verhagen is a dedicated mother and patriot who continuously risks her life to hide displaced people in the family windmill. She manages the household during severe food shortages and teaches her children that conventional morality sometimes must bend to protect innocent lives.

Uncle Cor is Mrs. Verhagen's brother and an active member of the Dutch Underground. He organizes weapons drops, hides allied soldiers, and relies heavily on creative disguises to move around the countryside unnoticed. He regularly utilizes the help of younger citizens to deliver messages and coordinate resistance efforts.

Reina is the niece of the local doctor who secretly works as a courier for the Underground. She delivers illegal newspapers that counter German propaganda and coordinates with other resistance members to warn them of impending raids. She is strong-willed and fiercely fights back when threatened.

Hendrik is the younger brother of the local landwatcher, Leendert. He visits the Watchman to learn about its mechanisms but proves himself untrustworthy by lying about his ability to swim and thoughtlessly repeating sensitive information.

Charles is a British aviator whose bomber is shot down during an aerial battle. Separated from the rest of his crew, he hides in an old, abandoned mill while hoping to connect with the local resistance to escape the occupying forces.

Freya is a dog rescued by Joris at the beginning of the summer. She grows into a fiercely loyal companion who alerts the Verhagen family to unwanted visitors and actively protects the windmill from intruders.

Father Kobus is the local priest who provides spiritual guidance to the community during the occupation. He preaches that individuals must work to overcome the evil inside them and encourages his parishioners to help their neighbors in perilous times.

Hildebrand is a former university student who escapes custody during an aerial raid. He takes refuge with the Verhagen family, where he spends much of his time studying old texts and offering philosophical perspectives on the nature of war and retribution.

Koba is a young girl from the city who comes to live with the Verhagens to avoid starvation. She quickly acclimates to the family's daily routine and eagerly anticipates traditional holidays despite the ongoing war.

Betsy is Koba's sister, relocated from the city to the countryside for safety and food security. She joins the Verhagen household and brings a sense of childhood normalcy to the tense environment.

Trixie is a young girl living as part of the Verhagen family. She was left behind as an infant when her neighbors were deported, and the Verhagens have raised her under a false identity to ensure her survival.

Dr. de Vries is the local physician who treats injuries and illnesses in the community. He supports the underground movement by providing cover and clothing for fugitives trying to escape the area.

Mrs. Groen is a neighbor of the Verhagens who was deported three years prior. She maintains a connection to the Verhagen household through the young child she was forced to leave behind.

Mr. Poot is a local farmer who uses a clever hiding place to shelter allied aviators. His arrest serves as a harsh reminder to the community of the dangers involved in defying the occupying forces.

Engel is a friend of Dirk Jan who helps the Verhagen family evade the strict rules imposed by the occupying forces. He loans out his family's elderly dog to help secure a safety tag for Freya.

Gerardus is a member of the Underground in the city of Leyden. He receives coded messages about weapons drops and coordinates the logistics with other resistance members.

Van Loo is an assistant miller who works at the Falcon. He possesses the technical knowledge and strength required to position the windmill's wings into specific formations to send coded messages across the countryside.