They weren't particularly close until Peter's family joined Anne's in hiding, but they were aware of one other's existence. Peter had heard of an event in which Anne's instructor referred to her as Mrs. Quack Quack, and he uses the moniker to mock Anne when she irritates him. I heard about you, Peter. Because you spoke so much in class, they dubbed you Mrs. Quack Quack.
Peter and Anne eventually become friends, and when she needs someone to talk to, she comes to him. He calls her Mrs. Quack Quack because she talks so much.
Quack Anne's instructor nicknamed her "Quack" because she wouldn't stop chatting in class. As a punishment, he chastised her and assigned her an additional writing task. Peter, who went to the same school as Anne, had heard about it and ridiculed her about it. She is shocked and humiliated that he would bring it up. He has just found out that she is hiding behind a screen name and doesn't want anyone to know that she is Anne Frank.
Later, when Anne asks Mr. van Daan why he hates Jews so much, he says it's because Jesus told him to. This makes Anne uncomfortable and she tries to explain that Jesus was Jewish too but he won't listen. Later, when Peter comes to visit her in her hideout, she tells him what Mr. van Daan said and that it wasn't right of him to accuse someone he didn't even know of being a Jew. Peter tells her not to worry about it and they have dinner together. The next day, when Anne's family goes into hiding, she writes in her diary that she is afraid she will never see Peter again.
After several months, the van Daans are discovered by the Nazis and they all go into hiding again. Mr. van Daan gives himself up to save his wife and children but is sent to a concentration camp where he dies. Mrs. van Daan takes her children to Switzerland where they live happily ever after.
Peter and Anne are now more open about talking about their feelings and sharing each other sensitive things they wouldn't tell a stranger. Peter and Anne are clear about their goals for their lives. Peter tells Anne how calm she is now in comparison to the beginning of the concealment. They also talk about what might happen if either of them found out that the other was still hiding something.
Anne says that she doesn't want her family to worry about her, but she doesn't think she can keep hiding this from them forever. She thinks it's best if she goes to London to continue her training as a spy. She wants to know what Peter thinks about this. He tells her he understands why she needs to go and he hopes she gets selected for the agency soon so they can talk about planning their future together.
After saying goodbye to her family, Anne heads off to London to begin training with the agency. She believes she will be able to use her skills to help protect America from further attacks.
In January 2002, after completing her training, Anne returns home to California where she finds that her family has been without any news of her for months. She decides to contact the agency to see if there's anything new with Peter. It turns out that he was recently injured in a car crash at the hands of one of his patients. The patient died but Peter survived.
Both Peter and Anne don't get along with their moms, owing to the generation gap that exists between mothers and teens. Peter feels humiliated by his mother because she flirts with Mr. Frank and disputes with his father in public. Mrs. Van Daan also makes light of Peter and Anne's relationship, which embarrasses him. Finally, Peter runs away from home.
Anne's mother is too strict with her. When Mrs. De Beukelaar lets herself be persuaded to dance with Mr. Frank at the town ball, this disappoints Anne who had expected her mother to refuse him. Later on, when Mrs. De Beukelaar tells some stories about her life in Indonesia to the other women at the dinner table, this also upsets Anne who thinks these stories are vulgar and inappropriate. Finally, when Mrs. De Beukelaar refuses to let her wear shoes to meet the requirements for marriage, this further angers Anne.
Peter's parents divorce when he is a young boy, and he does not understand why his mother doesn't fight for his father's attention. He also finds his father too indulgent with his wife and seems to like having two wives himself. This makes Peter feel insecure about his position as the only son in the family.
When Peter turns 15, he is able to work part-time and help his parents pay the rent. However, since he is still a child at heart, he gets bored easily and needs to have fun sometimes.