Mattia Pascal, a former book keeper in the library, bequeathed by a certain Signor Boccamazza to his hometown, writes the story of his life. Mattia's father died early, and the mother was left with two children - six-year-old Roberto and four-year-old Mattia. All matters were managed by the manager Batta Malagna, who soon ruined the family of the former owner. After the death of his first wife, a middle-aged Malanya married a young Oliva, to whom Mattia was not indifferent, but they had no children, and Malanya began to offend Oliva, considering her to blame for this. Oliva suspected that the matter was not in her, but in Malanya, but decency prevented her from checking her suspicions. A friend Mattia Pomino told him that he was in love with the cousin of Malany Romilda. Her mother wanted to marry the rich girl Malanya, but this did not work, and now, when Malanya began to repent of her marriage to the childless Oliva, she is plotting new intrigues. Mattia wants to help Pomino marry Romilda and makes acquaintance with her. He always tells Romilda about Pomino, but the lover himself is so timid that in the end she does not fall in love with him, but with Mattia. The girl is so good that Mattia can not resist and becomes her lover. He is going to marry her, and then she suddenly breaks with him. Oliva complains to Matthia’s mother about Malanya: he received evidence that they have no children through no fault of his own, and triumphantly told her about it. Mattia understands that Romilda and her mother vilely deceived him, and Malanya, and in return makes Olive a child. Then Malanya accuses Mattia of having dishonored and destroyed his niece Romilda. Malanya says that out of pity for the poor girl, he wanted to adopt her child when he was born, but now that the Lord sent him a consolation of a legitimate child from his own wife, he can no longer call himself the father of another child who will be born to his niece. Mattia remains stupid and forced to marry Romilda, as her mother threatens him with a scandal. Immediately after the wedding, Mattia’s relationship with Romilda deteriorates. She and her mother cannot forgive him that he has deprived his legitimate child, for now the whole state of Malanya will pass to the child of Oliva. Twin girls are born in Romilda, in Oliva - a boy .. One of the girls dies in a few days, the other, to whom Mattia manages to become very attached, does not live to see a year. Pomino, whose father becomes a member of the municipality, helps Mattia to get a librarian's position in the Boccamazzi library. Once, after a family scandal, Mattia, who accidentally had a small amount of money in her hands that neither her wife nor her mother-in-law knew, leaves home and leaves for Monte Carlo. There he goes to a casino, where he wins about eighty-two thousand lire. The suicide of one of the players makes him change his mind, he stops the game and goes home. Mattia imagines how his wife and mother-in-law will marvel at the unexpected wealth, he is going to buy the mill in Stia and live quietly in the village. Having bought the newspaper, Mattia reads it on the train and stumbles upon an ad that a dead corpse was found in his hometown in Mirano, in the mill gate in Stia, in which everyone recognized the librarian Mattia Pascal, who disappeared a few days ago. People believe that the cause of suicide was financial difficulties. Mattia is shocked, he suddenly realizes that he is completely free: everyone considers him dead - that means he now has no debts, no wife, no mother-in-law, and he can do whatever he pleases. He rejoices at the opportunity; to live two lives, as it were, and decides to live them in two different guises. From his former life, he will only have a squinting eye. He chooses a new name for himself: from now on his name is Adriano Meis. He changes his hairstyle, clothes, comes up with a new biography, throws out the engagement Ring. He travels, but is forced to live modestly, as he must stretch his money for the rest of his life: the lack of documents deprives him of the opportunity to enter the service. He cannot even buy a dog: taxes must be paid for it, and for this, documents are also required.
Mattia decides to settle in Rome. He rents a room with Anselmo Paleari, an old eccentric who is keen on spiritualism. Mattia is imbued with great sympathy for his youngest daughter Adriana - a modest kind girl, honest and decent. Adriana's son-in-law Terencio Papiano after the death of his sister Adriana must return Anselmo's dowry, since his wife died childless. He asked Anselmo for a delay and wants to marry Adrian so as not to return the money. But Adriana is afraid and hates the rude prudent son-in-law, she falls in love with Mattia Pascal. Papiano is sure that Mattia is rich, and wants to introduce him to the enviable bride - Pepita Pantogada, in order to distract him from Adriana. He invites Pepita to Anselmo for a seance. Pepita comes along with the governess and the Spanish artist Bernaldes.
During the seance, in which all the inhabitants of the house take part, at Mattia, twelve thousand lire disappear from the locker. Only Papiano could steal them.
Adriana invites Mattia to report to the police, but he cannot report the theft - after all, he is no one who has come to life. He cannot marry Adrian, no matter how much he loves her, because he is married. To hush things up, he prefers to lie, as if the money was found. In order not to torture Adriana, Mattia decides to behave so that Adriana will stop loving him. He wants to start caring for Pepita Pantogada. But the jealous Bernaldes, by whom Mattia accidentally offended, insults him, and the code of honor obliges Mattia to challenge Bernaldes to a duel. D Mattia cannot find seconds - it turns out that for this you need to follow a bunch of formalities, which is impossible to do without documents.
Mattia sees that his second life is at an impasse, and, leaving a cane and a hat on the bridge, so that everyone thinks that he rushed into the water, gets on the train and goes home.
From Adriano Meis he only has a healthy eye: Mattia has undergone surgery and no longer mows.
Arriving at home, Mattia first visits his brother Roberto. Roberto is shocked and does not believe his eyes. He tells Mattia that Romilda, after his alleged suicide, married Pomino, but now her second marriage will be legally considered invalid and she must return to Mattia. Mattia does not want this at all: Pomino and Romilda have a little daughter - why destroy their family happiness? And he doesn’t like Romilda. Pomino and Romilda are amazed and confused when they see Mattia alive, after more than two years have passed since his disappearance. Mattia reassures them: he does not need anything from them.
On the street no one recognizes Mattia Pascal: everyone considers him dead.
Mattia goes to the cemetery, looks for the grave of the unknown, which everyone took for him, reads the felt inscription on the grave stone and puts flowers on the grave.
He settles in the house of his old aunt. From time to time he comes to the cemetery "to look at himself - dead and buried. Someone curious asks; “But who will you be?” In response, Mattia shrugs, squints and answers: “I am the late Mattia Pascal.”
With the help of don Ellio, who succeeded Mattia as the curator of books in the Bokkamaodi library, Mattia lays out his strange story on paper for six months. In a conversation with don Ellio, he says that he does not understand what morality can be drawn from it. But don Eligio objects that there is no doubt a morality in this story, and this is what it is: “Outside of the established law, outside of those particular circumstances, joyful or sad, which make us ourselves ... it’s impossible to live.”
