Number the Stars opens with a street scene in Copenhagen. Annemarie, her younger sister Kirsti, and her best friend Ellen Rosen race home from school. On the way, two German soldiers stop them. Annemarie is disgusted by the fact that the soldier's Danish is so poor after three years of occupation. The soldiers interrogate the girls. Annemarie does most of the talking. The soldiers let the girls go, warning them not to run any more because it makes them "look like hoodlums." In silence, the girls walk home as quickly as possible. They reach the building where their families live, careful to avoid notice by another pair of soldiers on their corner. As they part, Ellen admits that she was scared and Annemarie says she was, too. They agree not to tell their mothers about the incident.
In the Johansen's apartment, Mrs. Johansen and Mrs. Rosen are waiting for their daughters to arrive. The women are drinking what they call coffee, which is actually only herbs in water because of the rationing. Kirsti gets to the door first and tells her mother what happened, exaggerating the story. Both mothers are concerned. Mrs. Johansen explains to Mrs. Rosen that the soldiers are "edgy because of the latest Resistance incidents." Annemarie pretends not to be listening to the discussion. Her mother whispers that their friend Peter Neilsen has brought the illegal Resistance newspaper, De Frie Danske (The Free Danes). The girls are to take a different route to school from now on. Mrs. Rosen leaves to talk to her daughter Ellen.
The girls are hungry, but there is little to eat. They have bread, but no butter. Kirsti longs out loud for a cupcake. Mrs. Johansen gently explains to her daughter that there is no sugar and there will be none until the war ends and the soldiers leave.
As they go to bed, Annemarie tells Kirsti a story. Kirsti wants to hear about kings and queens, but she falls asleep as soon as Annemarie begins. Annemarie thinks about the real king of Denmark, Christian X. He is different from fairy tale kings, but the people love him. Annemarie remembers the days when her older sister Lise would take her to see King Christian go through the streets on his horse, greeting people. Thinking of Lise saddens Annemarie. Lise died several years ago. Annemarie thinks of a story her father told her about running an errand not long after the occupation had begun. A German soldier saw King Christina coming on his horse, and asked a young man near him who it was. Upon hearing that it was the king, the soldier asked where his protection was, and the young man answered, "All of Denmark is his bodyguard." Annemarie remembers how her father told her he would die to protect the king and so would Mrs. Johansen. Annemarie said she would die for him, too. She had asked why the king wasn't able to protect them from the Nazis. Her father explained that Denmark is a very small country, and other countries that fought were crushed. Annemarie replied that Sweden was not occupied. She remembered seeing Sweden from the shore at her Uncle Henrik's house.
In bed, Annemarie considers how things have changed since the time when her father told the story of the soldier and the young man. Sweden is still free and King Christian is still alive, but her sister Lise is dead. Lise had died in an accident two weeks before she was to marry Peter Neilsen. Annemarie looks at the blue trunk in the corner of her room. It is filled with Lise's trousseau, the linens and goods she was to use as a married woman. Mr. and Mrs. Johansen do not speak of Lise. Peter has not married anyone, and has become serious despite his youth. When Peter comes to the apartment, he talks to Mr. and Mrs. Johansen about things Annemarie does not understand. Annemarie thinks about how her father has changed, too. The only thing that has stayed the same, she concludes, is fairy tales.
From the first moments of Number the Stars, Lowry explores the difficulty of understanding war when you are a child. Even Annemarie's most prosaic experiences—running down the street, for example—are colored by the Second World War. Though Annemarie is not the narrator of the novel, Number the Stars is told from her point of view. Much of the novel is filled with her thoughts and feelings about the events surrounding her. It becomes clear that Annemarie is a particularly pensive child, made more so by the environment she is growing up in.