Act 1
The Diary of Anne Frank begins in November 1945 with Otto Frank returning to the attic rooms where he, his family, the Van Daans, and Mr. Dussell hid during the Nazi occupation of Holland. He enters carrying a rucksack and moves slowly around the room, picking up a scarf and placing it around his neck. As he bends to retrieve a glove, he breaks down in tears. Hearing his sobs, Miep Gies comes upstairs, asking if he is all right and urging him not to stay in the rooms. Mr. Frank explains that he has come to say goodbye and is leaving Amsterdam, though he is unsure of his destination. Before he leaves, Miep hands him a stack of papers left behind after the Gestapo arrested everyone. Mr. Frank tells her to burn them, but Miep insists he look through them. She places Anne’s diary in his hands. Mr. Frank opens the diary and begins reading the first entry, dated July 6, 1942, aloud. Gradually, Anne’s voice joins his, and then Mr. Frank’s voice fades. Anne describes the worsening conditions for Jews in Holland after the German invasion. Her diary details the Franks’ last morning at home, as they tried to make it appear they had fled the country when, in fact, they went into hiding in the building where Mr. Frank had his business.

The next scene shifts to July 1942 in the attic where the families will hide. The Van Daans are waiting for the Franks. When the Franks arrive, accompanied by Miep and Mr. Kraler, the families introduce themselves; except for the men, no one knows each other. After Miep and Mr. Kraler leave to prepare for work, Mr. Frank explains the rules: during the day, when the workers are downstairs, they must not move, speak above a whisper, or run water. The families then begin to settle in and unpack their few possessions before the workday starts. Anne tries to get to know Peter and discovers they went to the same school, but she quickly notices how shy he is. On this first day in hiding, Mr. Frank gives Anne the diary.

Two months have passed. It's now six o'clock, and everyone is free to move around. Anne has taken Peter’s shoes, and when he tries to retrieve them, they end up in a playful tussle. Peter retreats to his room, leaving Anne wishing he were more playful. As Anne dances around, she accidentally spills milk on Mrs. Van Daan’s fur coat, causing Mrs. Van Daan to leave the room in a fury. Mr. Van Daan follows her, and Mrs. Frank advises Anne to be more considerate of their guests, reminding her that everyone is under significant stress. She suggests Anne should emulate Margot, who is more reserved. Anne then runs to her room.

Once alone, Mrs. Frank and Margot begin preparing supper. Mrs. Frank confides that she had asked Mr. Frank not to invite the Van Daans to share their hiding place, but he had insisted. Just then, the buzzer sounds, signaling the arrival of Mr. Kraler or Miep. Mr. Kraler enters with a request: Miep’s boyfriend has a Jewish friend who needs a hiding place. Can Mr. Dussel stay with them for a few nights? Mr. Frank immediately tells Mr. Kraler to bring Mr. Dussel upstairs, and he will share Anne’s room. Mr. Frank serves cognac to welcome Mr. Dussel. Mr. Dussel updates them on the situation in Amsterdam since they went into hiding. The initial news is positive; people believe the Franks have escaped to Switzerland. However, he also shares the grim reality that hundreds of Jews are sent to death camps daily, including Anne’s friends. Mr. Frank halts the conversation, and Anne shows Mr. Dussel to the room they will share.

In the following scene, Anne's screams from a nightmare wake everyone. Her parents rush to her room, but Anne sends her mother away and asks her father to stay. Anne confides in her father that he is the only person she loves. Mr. Frank explains that her rejection deeply hurts her mother. Anne feels she cannot control her behavior but immediately feels remorseful and asks her father what is wrong with her.

It's the first night of Hanukkah in 1942. Anne has thoughtfully prepared gifts for everyone, including the scarf Mr. Frank discovers in the play’s opening scene. Her creativity and consideration impress and touch everyone. However, the cheerful atmosphere is disrupted when Mr. Van Daan and Peter start arguing about Peter's cat. The argument is abruptly interrupted by a loud crash from the offices below. Instantly, everyone becomes silent and removes their shoes. While attempting to turn off the overhead light from a chair, Peter falls. The sound of running footsteps is heard from below. In the attic, everyone is terrified, fearing it might be the police coming to arrest them. Mr. Frank goes downstairs to investigate and returns with the news that it was a thief. Although he assures them the danger has passed, Mr. Dussel points out that now someone knows there are people hiding above the offices. To lift their spirits in the face of this new threat, Mr. Frank asks Anne to sing the Hanukkah song, and soon everyone joins in.

Act 2
Act 2 begins in January 1944; the families have been in hiding for nearly a year and a half. Miep and Mr. Kraler arrive with a New Year’s cake. Despite his wife's objections, Mr. Van Daan gives Miep his wife’s fur coat to sell. Mr. Kraler asks Mr. Frank to come downstairs to discuss some contracts, but Mr. Frank realizes that Mr. Kraler wants to speak privately. He insists Mr. Kraler speak in front of everyone, and they learn that an office worker is blackmailing Mr. Kraler, threatening to reveal the hidden room upstairs. Distressed and angry, Anne lashes out at her mother and retreats to her room. Peter follows her, reassuring her that he thinks she is fine. For the first time since going into hiding, Peter and Anne have a heartfelt conversation, forming a new friendship.

Anne and Peter’s growing friendship causes tension between their mothers. Mrs. Van Daan insinuates improper behavior whenever Anne visits Peter's room after dinner. Alone, Anne and Peter discuss various topics and share their first kiss. Meanwhile, general tensions in the cramped attic escalate. One night, these tensions explode when Mrs. Frank catches Mr. Van Daan stealing food. Mrs. Frank loses her temper, demanding that Mr. Van Daan leave the attic. Mr. Frank tries to calm her, but she is beyond reasoning. The crisis is interrupted by Miep’s arrival with the welcome news that the Allied invasion of the European continent has begun.

A few weeks later, everyone is gathered tensely in the central room. The office phone downstairs rings for the third time. Mr. Dussel insists it's a warning from Miep, who hasn't visited them for three days. No one has shown up for work downstairs either, another troubling sign. Mr. Dussel, backed by Mr. Van Daan, pleads with Mr. Frank to answer the phone, but Mr. Frank refuses. Mr. and Mrs. Van Daan start arguing, prompting Peter to retreat to his room. Anne follows him and talks about what they'll do once they're free. Suddenly, a car pulls up in front of the building. The outside bell rings repeatedly, followed by the sound of a door being forced open. They hear heavy footsteps and another door being broken down. It is the Nazis. “For the past two years we have lived in fear,” Mr. Frank says. “Now we can live in hope.” They hear the door to their stairwell being smashed in and the sound of German voices.

The play’s final scene shifts back to November 1945. Mr. Kraler has joined Miep and Mr. Frank in the upstairs rooms. Mr. Frank closes Anne’s diary. Mr. Kraler reveals that it was the thief who reported them. Mr. Frank shares that Anne was happy at the concentration camp, glad to be outside in the fresh air. Of the eight who hid in the attic, Mr. Frank is the sole survivor. After Auschwitz was liberated in January, Mr. Frank returned to Holland, learning about the deaths of his family and friends along the way. Only the day before, he had discovered Anne’s death at Bergen-Belsen. Anne’s voice, reading from her diary, brings the play to a close: “In spite of everything, I still believe that people are really good at heart.”