Peter is a member of the Resistance.
Peter Neilsen is a family friend. He was engaged to Annemarie’s older sister Lise, who died. The Johansens still love Peter, and consider him like a son. He visits them occasionally.
Annemarie is surprised when her parents ask her to come see Peter late at night. She knows that Peter being there is unusual, and that he should not be out at night. She is glad to see him, but worried about why he is there.
There was something frightening about his being here at night. Copenhagen had a curfew, and no citizens were allowed out after eight o'clock. It was very dangerous, she knew, for Peter to visit at this time. (Ch. 3)
Annemarie says Peter is thoughtful and always brings her gifts. There is more to Peter’s visits than just catching up with the family of his former fiancé. Peter brings the Johansens news, and works with them in the Resistance efforts. For example, he helps them get the Rosens to safety.
"We couldn't take all three of them. If the Germans came to search our apartment, it would be clear that the Rosens were here. One person we can hide. Not three. So Peter has helped Ellen's parents to go elsewhere. We don't know where. Ellen doesn't know either. But they are safe." (Ch. 16)
Being a member of the Resistance is very dangerous, even though Denmark is working secretly against the Nazi occupation. Peter is brave and effective. His role in saving the Rosens and other Jews is an important one. Peter tells Annemarie that the reason the Nazis are closing Jewish stores is to spread terror. He is determined to resist in any way possible.
Peter probably continues to be close to Annemarie’s family because he is mourning Lise. However, the Johansens are also brave and willing to help in the Resistance efforts, such as the night where they hosted the coffin of “Great-aunt Birte.” They are a useful contact for him.