In 1944, Joris Verhagen is 10 years old. His brother, Dirk Jan Verhagen, is 14. Together, the two boys live with their mother and father in a windmill called the Watchman. Dirk Jan is old enough to remember when everything was still plentiful before World War II. Now, however, the Germans have left Dutch citizens with very little, and their world has grown dangerous. 

At the start of the summer, Joris saves a puppy from the abuse of the de Wit boys. He races away with the animal, but when he returns home to the windmill, Mother insists that he return the dog. Father proposes that they purchase the puppy in order to save it, so they head to the Schenderhans family’s farm, where the de Wits are currently visiting. As they walk, their path takes them through their polder, “a piece of reclaimed land” that “has its own [wind]mill” (6)—the so-called “Watchman.” The Schenderhans live in a neighboring polder that has two windmills: the old, abandoned Giant and a new electric windmill. Father worries that the shift to electric mills will make the Watchman obsolete.

Mr. and Mrs. de Wit are happy to sell the dog. As the two families finalize the deal, Leendert Schenderhans, the eldest Schenderhans son, enters, and the room immediately becomes tense. The young man announces that he is now a landwatcher for the Germans; he even threatens to report his own father. 

Once the Verhagens leave, they see Hendrick Schenderhans, Leendert’s younger brother, hugging his own dog, Nero, whom Leendert has just kicked. Joris names his dog Freya. Because it is now past curfew, the Verhagens walk home cautiously, remaining alert.

Mother is distraught to learn that Leendert is now a landwatcher who reports to the occupying Germans; she regards his parents as good Catholics. Father retorts that people should be judged by what they do outside of church, not inside of it. 

One afternoon, Leendert struts around in his new uniform and encounters a young girl on a bike. Because bicycles are forbidden under the rules of the German occupation, Leendert demands that the girl hand the bike over to him. When she refuses, Leendert seizes the bike. The girl flings her satchel into the bushes and jumps at him, kicking him with considerable strength. Leendert hurls her to the ground, and she hits her head and remains motionless. Panicked, Leendert pedals away.

Joris and Dirk Jan happen by just in time to giggle at Leendert, but when they see the girl lying in the road, Joris runs to Dr. de Vries’s house to get help while Dirk Jan stays with her. When the doctor arrives, he is distraught to realize that the wounded girl is his niece, Reina. After Joris carts her to the doctor’s house, he returns to the scene to find Reina’s satchel spilling over with illegal newspapers. Nervously, Joris grabs the bag and cautiously returns it to Dr. de Vries. Then, Joris races home to the safety of the family windmill.

but Joris warns against it. However, Joris shows off by leaping onto one of the wings when it comes down; he then jumps off before it rises too high. Hendrik is not impressed, so Joris explains that a person could fall to their death if they rode the wing all the way around. Then, he describes the way the windmill functions, stating that it pulls water from the polder and then expels the water into a drainage canal.

After seeing a boat in the canal, Hendrik tells Mr. Verhagen that he can swim, so the boys are allowed to row to the Giant, the abandoned mill. The ride is peaceful until bombers suddenly roar overhead. When a burning plane crashes, the boys see four parachutes floating down onto the polder, and they jump ashore to watch. The Germans surround the plane and search for survivors. As Joris prays that the pilots escape, Hendrik returns to the boat. He falls into the water and shouts for help because he cannot swim. Joris saves him and is surprised that Hendrik lied about knowing how to swim. Hearing the commotion, the Germans rush over but are disappointed when they realize that the boys are not the pilots they are seeking. The boys head home, and when Hendrik claims that he was only pretending to need help in the water, Joris decides that Hendrik simply cannot be trusted.

A few days later, the Verhagens learn that a nearby farmer, Mr. Poot, and his son were seized by the Nazis for hiding three British pilots. The German soldiers also injured Mrs. Poot, and Father and the boys rush over to check on her. Dr. de Vries says that she will heal, but she is grieving the capture of her family. They all inspect the barn, and when they discover a clever hiding place that is only visible to the Schenderhanses’ farm, they assume that Leendert must have reported the presence of the three aviators. Suddenly, Joris remembers that there were four parachutes, not three.

Back home, Joris takes Freya to gather mushrooms. While wandering close to the Giant, he leaves Freya outside and enters the abandoned mill. Inside, everything is dusty and dirty. Despite his urge to leave, he ascends a staircase. On the first landing, a cat jumps into his arms, and he suddenly hears a creak. Remembering his father’s advice to confront his fears rather than avoiding them, Joris continues upstairs. On the top floor, he discovers broken machinery and old sails. As he looks underneath, a figure darts past. It is the fourth aviator, holding a pistol. Lowering the gun, the man smiles and introduces himself as Charles King. He pantomimes that he is hungry and that he needs new clothes. Joris understands and hurries away, remembering that Hendrik also knows that there were four parachutists.

When Joris gives his mother the mushrooms, she worries that the family will not have enough food if the country is not liberated soon. Sensing her fear, Joris does not mention Charles. He pretends to be hungry, and Mother chastises him for being greedy before offering a few cold potatoes. He hides them and decides not to tell his parents anything about the British pilot, for fear that they may be taken away like Mr. Poot was.

At dinner, Father talks about Kees Kip, the hero of the Dutch Underground; Kees Kip pretended to be an SS officer so that he could destroy documents and protect Dutch citizens from deportation. Nobody knows who Kees Kip is, but he is revered across Holland. Mother also worries about her brother, Cor, as he also works for the Underground. 

Later, Joris gathers more food from their garden. In bed, he waits for Dirk Jan to go to sleep and dwells on an incident that occurred three years ago, when he witnessed the Groen family being taken away by the Germans. When this happened, Mrs. Groen mouthed something to Joris’s mother, who later found a baby hidden in the bushes. They called her Trixie and pretended that she was a member of the Verhagen family. When Joris asked about the Germans, Mother instructed him according to the tenets of her own faith, saying that they must love everyone, even their enemies. However, when she admitted that she could not love the Germans, Joris realized that even adults struggle to do what is right. Afterward, Joris had nightmares about the Germans taking his family.

Now, Joris shakes away these memories and gets up quietly. He puts on his clothes, locks Freya inside, and grabs the food for Charles. Outside, the moon shines brightly, and bombers drone above as Joris walks to the Giant to deliver the food to Charles.

The world seems strange in the dark, and Joris perceives the sound of footsteps behind him. When he arrives at the Giant, he knocks on the door. Faint with hunger, Charles eats the offered food quickly, but a sudden noise forces him to hide. A person eases inside and sneezes, and Joris recognizes Dirk Jan. After meeting Charles, Dirk Jan speaks in English, explaining where they are and telling Charles that the other aviators were captured. Charles vows revenge, but Dirk Jan says that they have no weapons. However, the pilot argues that they have “right on [their] side [which is] the biggest weapon” (55). Dirk Jan urges Charles to stay inside until they can get him new clothes.

When the Schenderhans celebrate the fact that the Germans are losing, Leendert insists that the news is wrong and that the Germans are too clever to lose. As evidence for his argument, he cites their capture of the pilots. Without thinking, Hendrik blurts that there must be another aviator because he saw four parachutes. Leendert storms out, vowing to find the fourth man.

At Confession on Saturday, Joris admits to lying, stealing, and sneaking out. Then, he and Dirk Jan visit Reina, who has recovered and is excited to learn about Charles. She declares that Kees Kip dressed as a woman once in order to escape; she suggests that they ask her uncle for an extra dress for Charles. Later, the boys do just that, and Dr. de Vries provides one that used to belong to his late wife. 

At home, Joris and Dirk Jan learn that Leendert has been asking about a fourth aviator. Remembering his Confession, Joris reveals that he and Dirk Jan have been helping the pilot. His parents are pleased.