The play opens on July 6, 1942 in Amsterdam. Because they are Jews, the Frank and van Daan families move into hiding to avoid arrest by the Nazis. Mr. Kraler and Miep Gies, Christian business associates and trusted friends, help everyone get settled in the secret annex: Mr. and Mrs. Frank and their daughters, Margot and Anne, as well as Mr. and Mrs. van Daan and their son, Peter. The outsiders leave, assuring the two families that they will help them in hiding for as long as it takes. As the families begin to unpack, Anne tries to get acquainted with the shy Peter. Over all this are the haunting words from Anne’s diary.
Months pass, and Anne's carefree nature begins to cause problems. Mrs. Van Daan thinks she is rude, Margot is becoming distant, and Peter (her only hope for a friend) is very shy. In addition, her relationship with her mother is very strained.
Next, Mr. Dussell joins them in the annex and tells them what has been happening since they went into hiding. They are relieved to hear that people believe the Franks escaped to Switzerland, but are terrified when they learn of the death camps that hundreds of Jews are sent to each day.
Soon, it is their first Hanukkah in hiding, and Anne is determined to celebrate. She has thoughtfully prepared presents for everyone. However, the good mood is broken when Mr. Van Daan and Peter start arguing. The argument is quickly ended by a crashing sound in the offices below. Fearing they will be discovered, everyone immediately quiets down. From below comes the sound of running feet. Mr. Frank goes downstairs to investigate and returns with the news that it was a thief—but everyone is now even more on edge.
Over many more months, Anne and Peter’s young teenage friendship begins to blossom. They talk of all sorts of things, and they share their first kiss. Yet, tensions in general are growing in the cramped quarters. The families learn from Miep that the Allied invasion of the European continent has begun, and they are hopeful that they may soon come out of hiding. However, only a few weeks later, the Nazis arrive to take them away. Anne writes the last entry in her diary on August 1, 1944.
The play ends with the return of Mr. Frank to the abandoned hiding place. He has Anne’s diary and tells the audience exactly what has happened to each of the characters.
Only Anne’s words remain.