The book starts describing the thirteenth birthday of Anne Frank, a Jewish girl living in Germany. It is June 12, 1942. Her parents give to her a diary as a present and Anne is excited because she wants a place to store all her secrets. Also Anne dreams to become a writer or start a career of a journalist and she decides that the diary becomes her first practice. Anne starts writing her diary entries as a letter to imaginary friend Kitty, someone who she can show her deepest feelings.
Anne’s family immigrated to Holland from Germany fearing for their lives. Mr. Frank - Anne’s father - got a job there, but still the rules for Jews were very strict and oppressive even there. They have to wear a yellow star on their clothes, shop and study in separate places and so on. The real horror starts when one day Anne’s older sister, Margot, is called by the authorities. That means she will be sent to concentration camp.
The family was preparing for this for a long time. They planned to move somewhere else, but now they have no time for it. So Mr. Frank moves everyone of the family into his office building, part of which is walled off and the door is hiding behind the bookcase. The company of Mr Frank named Travis Company is still loyal to him and people working there are willing to help his family. They pretend to work like nothing happened, serving as a decoy to the Franks’ hideout. Anne refers to this place as to “Secret Annex”.
A few days later another family joins them in their hiding, the Van Daans. They are a couple and their son Peter, who is slightly older than Anne. It becomes crowded inside the Annex and later another person comes, recommended by one of the Mr. Franks employees, Miep - Mr. Dussel, an elderly dentist who Anne now has to share her bed with. All the inhabitants of the Annex try to get along with each other, but, of course, under such stress of being locked from the outside world, not everyone succeeds in it.
Miep, her husband Henk, Elli and Mr. Koophuis are the supportive group of the families hiding in the Annex. The Franks and Van Daans treat them as an extension of their families, but these people are also the only source of food and other supplies and their only connection to the outer world.
Anne feels particularly miserable. She has to be silent during the daytime, sealed inside the tiny rooms of Annex and is constantly frightened by the loud sounds from the outside. She feels like whatever she does serves only as an extra reason for adults to berate her. They often have quarrels with Anna’s mother and the culmination of this comes when Mrs. Frank asks Anne to pray with her one night instead of Mr. Frank. Anne refuses, but her mother, despite her disappointment and sadness, tells her daughter that she will not force Anne to love her, or at least try not to do this.
To Anne’s luck there are lots of books in the Secret Annex and a radio. Anne grows up as a well-educated girl, knowing lots about politics, history, classic literature and so on. She sublimates her feelings into studying, saving herself for boredom and madness caused by isolation. At the same time she becomes more and more distant from the other family members.
The descriptions of relationships inside the Annex interchange with the brief depictions of the events in the outer world. Miep, Henk and other become ill and the disease progresses. The dwellers of the Annex are very worried. Not only they afraid that the disease will kill their friends who almost became their family, but if it happens they will lose the only source of food and everything essential for survival.
The house is also occasionally raided by burglars. Several times, they manage to break inside and all the families have to freeze in fear silently not letting anyone hear them and either kill them or report them to the Gestapo that also means death for most of them.
Anne grows up. She starts to see Peter van Daan as someone more than just a friend but still is unsure in her feelings. She spends a lot of time with him in the attic, far from the adults. At that time she confesses to her diary on having dreams about other boy she liked, also named Peter, Peter Schiff. Sometimes two Peters are even confused in her thoughts.
The girl trusts Peter van Daan most of the secrets, because he is calm, caring and sensitive. She trusts him and feels that it is safe to talk to him about everything, even most intimate things. Their relationship is a bit complicated, because Anne’s vision of him shifts from trusted friend to boyfriend, but nevertheless they find a source of mutual comfort in it.
Another prominent event for Anne is the rumor that the war will soon end. She hears the news that the diaries like hers will be in demand after it and even decides to start a novel called “Hidden Annex”. The tone of her notes become as optimistic as it was at the beginning of the diary, she is very excited and glad to hear every news possible. On September 10, 1943 Anne makes a record about fall of Italy, hoping that everything they have to endure will soon finish and everyone in the Annex will be able to return to the previous life.
The Van Daans are running out of money. They desperately hope to sell something of their possessions. Mrs. Van Daan has a luxurious fur coat and she doesn’t want to give it away at any circumstances. But this coat may be a lifesaver for the whole family. With great effort Mr. Van Daan convinces her to sell the fur coat and the family can finally buy (through their helpers from outside) food and other necessary things for themselves.
On June 6, 1944 the invasion starts, bringing the new burst of joy to the Annex inhabitants. They finally believe that it will soon be over and they even plan to leave in October 1944. To their disappointment it never happened.
Anne becomes more and more desperate. Hearing about suffering and atrocities going on in the world she feels that her own suffering is almost unbearable. She writes that she doesn’t feel valuable anymore, that everyone in the Annex and beyond it dislikes her and her relatives constantly criticize her. She even goes that far as thinking that it might be better for them all die instead of miserable life in the Annex. Anne becomes rough on others, but she is equally rough on herself, blaming herself of not being nice.
The last entry in her diary is about her two halves, the outer person, who is a cheerful and easygoing young girl and the inner one, troubled, tired, but still trying to grow up into a better person.
Then her diary ends. Two days after that entry the Secret Annex was discovered and raided. Every family member was sent to different concentration camps and after the war Otto Frank, the father of the family, was the sole survivor.
This diary accurately depicts the living and struggling of the families hiding in the Secret Annex but also it is the private log of a young girl on the edge of her adolescence.