In 1835 the family of Buddenbrooks, a highly revered family in the small German trading city of Marienkirche, moved to a new house on Mengstraße, recently acquired by the head of the firm "Johann Buddenbrook". The family consists of the old Johann Buddenbrook, his wife, their son Johann, daughter-in-law Elizabeth and grandchildren: ten-year-old Thomas, eight-year-old Antony - Tony - and seven-year-old Christian. With them still live Toni’s peer Klotilda, the offspring of the poor family line, and governess Ida Yungman, who served them for so long that is considered almost as a member of the family.
But the firstborn of Johann Buddenbrook, Sr., Gotthold, who lives on the Breiten Strasse, the family tries not to mention: he committed a misalliance, having married a shopkeeper. However, Gotthold himself did not forget about his relatives and requires the part of the purchase price of the house. Johann Buddenbrook Jr. oppresses enmity with his brother, but, as a businessman, he understands that if Hortkhodd is paid the required, the firm will lose hundreds of thousands of marks, and therefore advises the father not to give money. He readily agrees.
Two and a half years later, the house of the Buddenbrooks comes to joy: Elizabeth gives a birth to a daughter Clara. The happy father solemnly records this event in a notebook with a gold edge, begun by his grandfather and containing a long genealogy of the Buddenbrook family and personal records of the next head of the family.
And three and a half years later, the old Madame Buddenbrook dies. After this her husband retires from business, passing the management of the company to his son. And soon he also dies. Having met Gortholm at the grave of his father, Johann firmly refuses to him in the inheritance: in front of the debt that imposes on the head of the firm on all other feelings must be hushed up. But when Gotthold liquidates his shop and retires to rest, he and his three daughters are happily taken to the bosom of the family.
The same year Tom enters into his father's business. Tony, confident in the power of the Buddenbrooks and correspondingly in her own lack of independence, often upsets her parents with her pranks, and therefore she is sent to the boarding house of Zazemi Weichbrodt.
Tony is already eighteen years old, when Mr. Grünlich, a businessman from Hamburg, completely captivating her parents, makes her an offer. Tony does not like him, but neither his parents nor he himself accepts her refusal and insist on marriage. In the end, the girl is sent to Travemunde to the sea: let her come to her senses, reflect and make the best decision. She settles in the house of the old pilot Schwarzkopf.
The son of the pilot Morgen often spends time with Tony. Confident intimacy arises between them and soon young people confess to each other in love. However, after returning home Tony accidentally stumbles on a family notebook with a gold border, reads ... and suddenly realizes that she, Antonia Buddenbrook, - the link of a single chain and from birth is called to promote the exaltation of a kind. She grabbed the pen violently and wrote another line into the notebook - about her own engagement with Mr. Grünlich.
Tony is not the only one who goes against the dictates of the heart: Tom also has to leave his beloved, a saleswoman of the flower shop. Grünlich's family life is not very successful: Grünlich does not pay much attention to his wife, tries to limit her expenses. And four years later it turns out that he is a bankrupt: it could have happened before, not by chance he gets Tony with her dowry and creates an impression, that he works together with the firm of the father-in-law. Johann Buddenbrook refuses to help his son-in-law; he dissolves Tony's marriage and takes her along with her daughter Erica.
In 1855 Johann Buddenbrook dies. Supremacy in the firm actually goes to Thomas, although at his suggestion, his uncle Gorthold holds a fictitious position. Tom is a serious young man, who knows how to keep up appearances and who has a business sense. But Christian, although he spent eight years in foreign lands, learning to do business, does not show labor zeal and instead of compulsory sitting in the office of the family firm he spends his time in the club and the theater.
Meanwhile Clara is nineteen years old; she is so serious and god-fearing that it is difficult to marry her otherwise than as a person of spiritual rank, so Elizabeth Buddenbrook agrees without thinking about the marriage of her daughter with the pastor Tiburtius. Tom to whom after Gotthold's death passes the title of head of the family and the position of the head of the firm, also agrees, but with one condition: if mother allows him to marry Gerda Arnoldsen, Tony's friend at the boarding house, he loves her, and, his future father-in-law is a millionaire.
Both engagements are celebrated in a close family circle: besides the relatives of the Buddenbrooks, including the daughters of Gothold - three old maidens from Breitenstrasse and Clotilde, there are only Tiburtius, the Arnoldsen family and an old friend of the house Zazemi Weichbrodt. Tony introduces the history of the Buddenbrook family, reading out the family notebook. Soon two weddings will take place.
After that silence reigns in the house on Mengstrzasse: Clara and her husband will now live in his homeland, in Riga; Tony, having entrusted Erik with Zazemi Weichbrodt’s care is leaving to visit her friend in Munich. Clotilda decides to settle herself and moves to a cheap boarding house. Tom and Gerda live separately. The Christian, who is more and more idle and therefore increasingly quarrels with his brother, eventually leaves the company and joins a partner in one company in Hamburg.
Tony returns, but soon after her comes Alois the Permaneder, who she met in Munich. His manners leave much to be desired, but, as Tony says to her eternal attorney, Ide Jungman, his heart is kind, and most importantly - only a second marriage can make up for the failure with the first and remove the shameful stain from the family’s history.
But the second marriage does not make Tony happy. Permaneder lives modestly, and in Munich nativity of the Buddenbrooks is not respected. Her second child is born dead, and even grief can not bring the spouses together. And once Tony finds her husband when he, drunk, tries to kiss the maid! The next day Antonia returns to her mother and begins troubles about divorce. After that, it only remains for her to drag on the bleak existence of a divorced wife.
However to the family comes joy – Thomas’s son is born, the future heir of the company, named after his grandfather Johann, in short - Ganno. Ida Yungman begins to take care of him. And after a while Tom becomes a senator, having won the election of his old competitor in the trade of Hermann Hagenstrpm. The new-born senator builds a new magnificent house - a real symbol of the power of the Buddenbrooks.
And then Klara dies of brain tuberculosis. Fulfilling her last request, Elizabeth gives Tiburtius the hereditary share of her daughter. When Tom learns that such a large amount of money left the firm's capital without his consent, he is enraged.
In 1867, twenty-year-old Erika Grünlich marries Mr. Hugo Weinshenk, a director of the insurance company. Tony is happy. Although in the family notebook next to the name of the director is inscribed the name of her daughter, not her own, one might think that Tony is a bride - with such pleasure she is engaged in the arrangement of an apartment for young people and receives guests.
Meanwhile Tom is in deep dejection. The fact that all successes have passed, that he is at forty-two years a man of conscience, based more on internal conviction than on external facts, completely deprives him of energy. Tom tries to catch his luck again and starts up a risky fraud, but that, alas, fails. The firm "Johann Buddenbrook" gradually descends to a penny turn, and there is no hope for a change for the better. The long-awaited heir, Hanno, despite all the efforts of his father, shows no interest in the trade business; this sickly boy, like his mother, is fond of music. Once family notebook falls into the hands of Hanno. The boy finds there a genealogical tree and almost mechanically draws a line across the page below his name. And when the father asks him what it means, Hanno babbles: "I thought that nothing will happen later".
Erika's daughter Elizabeth is born. But the family life of Weinshenks is not destined to last long: the director, who did not do anything that most of his colleagues do not do, is accused of legal violation, sentenced to imprisonment and immediately taken into custody.
A year later, old Elizabeth Buddenbrook dies. Immediately after her death, Christian, who never managed to get accustomed to any company, idle and constantly complaining about his health, declares his intention to marry Aline Poufogel, a person of easy virtue from Hamburg. Tom resolutely forbids him.
A big house on Mengstraße is no longer needed by anyone, and it is sold. And Herman Hagenstrem buys the house, whose trading business, in opposition to the affairs of the firm "Johann Buddenbrook", is getting better and better. Thomas feels that he, with his constant doubts and fatigue, cannot return the family company the former glitter, and hopes that his son will do it. But alas! Hanno still shows only resignation and indifference. Disagreements with his son, deteriorating health, suspicion of his wife's infidelity - all this leads to a decline in strength, both moral and physical. Thomas anticipates his death.
Early in 1873, Weinshenk was released ahead of schedule. Even without appearing on the eyes of his wife's relatives, he leaves, informing Erika of his decision not to unite with his family until he can provide her with a decent life. No one will hear nothing of him.
And in January 1875, Thomas Buddenbrook dies. His last will - the firm "Johann Buddenbrook", which has a hundred-year history, should be finished within one year. The liquidation goes so hastily and unskillfully that from the condition of the Buddenbrooks, soon there are only crumbs left. Gerda is forced to sell a magnificent senator's house and move to a country villa. In addition, she fairs Ida Yungman, and she leaves for relatives. Christians departs soon - at last he can marry Alina Poufogel. And although Tony Buddenbrook does not recognize Alina as her relative, nothing can stop the latter from putting her husband in a closed clinic and taking full advantage of legal marriage, leading her former way of life.
Now the first place in the society of the Marienkirche is occupied by the Hagenstrems, and Tony Buddenbrook is deeply wounded by this. However, she believes that in time Hanno will return them the former greatness. Hanno is only fifteen years old when he dies of typhus.
Six months after his death Gerda goes to Amsterdam to her father, and together with her, the remains of Buddenbrook's capital and their prestige finally leave the city. But Tony and his daughter, Clotilde, the three ladies of Buddenbrook from Breitenstrasse and Zazemi Weichbrodt will still gather together to read the family's notebook and hope for the best.