In 1815 Edmond Dantès, a young and successful merchant sailor recently granted his own command by his dying captain Leclère, returns to Marseille to marry his fiancée Mercédès. Leclère, a supporter of the exiled Napoléon I, has charged Dantès to deliver two objects: a package to Maréchal Bertrand (exiled with Napoleon Bonaparte on Elba), and a letter from Elba to an unknown man in Paris. An anonymous letter accuses Dantès of being a Bonapartist traitor. Villefort, the deputy crown prosecutor in Marseille, normally a just man, condemns Dantès without trial to life imprisonment and destroys the incriminating letter.
During his fourteen years imprisonment in the Château d'If, Dantes befriends the Abbé Faria, ("The Mad Priest"), a fellow prisoner trying to tunnel his way to freedom who claims to be in possession of a massive treasure, offering to reward the guards well if they release him. Faria educates Dantès and, when he knows he is dying, tells Dantès the location of a treasure on Monte Cristo. After Faria's death the following year, 1829, Dantès stages an escape and is rescued by a smuggling ship. After several months of working with the smugglers, he goes to Monte Cristo. Dantès fakes an injury and convinces the smugglers to temporarily leave him on Monte Cristo, then makes his way to the hiding place of the treasure. After recovering the treasure, he returns to Marseilles, where he learns that his father has died in poverty. He buys a yacht, hides the rest of the treasure on board and buys both the island of Monte Cristo and the title of Count from the Tuscan Government.
Returning to Marseille, Dantès plans his revenge but first helps several people who were kind to him before his imprisonment. Traveling as the Abbé Busoni, he meets Caderousse, now living in poverty, whose intervention might have saved Dantès from prison. Dantès learns that his other enemies have all become wealthy since Dantès' betrayal. He gives Caderousse a diamond that can be either a chance to redeem himself, or a trap that will lead to his ruin. Caderousse murders the jeweler to whom he sells the diamond and is sentenced to life in the prison galleys. Dantès, using the disguise of English Lord Wilmore, frees Caderousse and gives him another chance at redemption. Caderousse does not take it, and becomes a career criminal. Learning that his old employer Morrel is on the verge of bankruptcy, Dantès, in the guise of a senior clerk, buys all of Morrel's outstanding debts and gives Morrel an extension of three months to fulfill his obligations. At the end of the three months and with no way to repay his debts, Morrel is about to commit suicide when he learns that all of his debts have been mysteriously paid and that one of his ships has returned with a full cargo, secretly rebuilt and laden by Dantès.
Now nine years later (1838), Dantes, disguised as the rich Count of Monte Cristo, takes his revenge on the three men responsible for his unjust imprisonment: Fernand, now Comte De Morcerf and Mercédès's husband; Danglars, now a wealthy banker; and Villefort, now married to his second wife and living in Paris. The Count surfaces first in Rome, where he becomes acquainted with the Baron Franz d'Épinay, and Viscount Albert de Morcerf, Mercédès's and Fernand's son. Dantès moves to Paris, and with Albert de Morcerf's introduction, becomes the sensation of the city. Due to his knowledge and rhetorical power, even his enemies, who do not recognize him, find him charming, and because of his status they all desire his friendship. Monte Cristo dazzles the crass Danglars with his seemingly endless wealth, eventually persuading him to extend him a 6,000,000 francs credit, and withdraws nine hundred thousand. Under the terms of the arrangement, Monte Cristo can demand access to the remainder at any time. The Count manipulates the bond market, through a false telegraph signal, and quickly destroys a large portion of Danglars' fortune. The rest of it begins to rapidly disappear through mysterious bankruptcies, suspensions of payment, and more bad luck on the Stock Exchange.
Monte Cristo threatens Villefort with knowledge of his past affair with Madame Danglars, which produced a son. Believing the child to be stillborn, Villefort had buried the child. The boy had been rescued and raised in Corsica by his enemy, Bertuccio (now Monte Cristo's servant), who gave the child the name "Benedetto". As an adult, Benedetto becomes a criminal who was sentenced to the galleys with Caderousse. After being freed by "Lord Wilmore", Benedetto takes the identity of "Viscount Andrea Cavalcanti" (sponsored by the Count) and cons Danglars into betrothing his daughter Eugénie to him. Caderousse blackmails Andrea, threatening to reveal his past. Cornered by "Abbé Busoni" while attempting to rob Monte Cristo's house, Caderousse begs to be given another chance, but Dantès grimly notes that the last two times he did so, Caderousse did not change. He forces Caderousse to write a letter to Danglars exposing Viscount Cavalcanti as an impostor and allows Caderousse to leave the house, but the moment Caderousse leaves the estate, he is stabbed in the back by Andrea. Caderousse manages to dictate and sign a deathbed statement identifying his killer, and Monte Cristo reveals his true identity to Caderousse moments before Caderousse dies.
Years before, Ali Pasha, the ruler of Yannina, was betrayed to the Turks by Fernand. After his death, his wife Vasiliki and his daughter Haydée were sold into slavery. Haydée was found and rescued by Dantès and becomes the Count's ward. The Count manipulates Danglars into researching the event, which is published in a newspaper. As a result, Fernand is brought to trial for his crimes. Haydée testifies against him, and Fernand is disgraced. Mercédès, still beautiful, alone recognizes Monte Cristo as Dantès. When Albert blames Monte Cristo for his father's downfall and publicly challenges him to a duel, Mercédès goes secretly to Monte Cristo and begs him to spare her son. During this interview, she learns the entire truth of his arrest and imprisonment. She later reveals the truth to Albert, which causes Albert to make a public apology to Monte Cristo. Albert and Mercédès disown Fernand, who is confronted with Dantès' true identity and commits suicide. The mother and son depart to build a new life free of disgrace. Albert enlists as a soldier and goes to Africa in order to rebuild his life and honour under a new name, and Mercédès begins a solitary life in Marseille.
Villefort's daughter by his first wife, Valentine, stands to inherit the fortune of her grandfather (Noirtier) and of her mother's parents (the Saint-Mérans), while his second wife, Héloïse, seeks the fortune for her small son Édouard. Monte Cristo is aware of Héloïse's intentions, and "innocently" introduces her to the technique of poison. Héloïse fatally poisons the Saint-Mérans, so that Valentine inherits their fortune. Valentine is disinherited by Noirtier in an attempt to prevent Valentine's impending marriage with Franz d'Épinay. The marriage is cancelled when d'Épinay learns that his father (believed assassinated by Bonapartists) was killed by Noirtier in a duel. Afterwards, Valentine is reinstated in Noirtier's will. After a failed attempt on Noirtier's life, which instead claims the life of Noirtier's servant Barrois, Héloïse then targets Valentine so that Édouard will finally get the fortune. However, Valentine is the prime suspect in her father's eyes in the deaths of the Saint-Merans and Barrois. On learning that Morrel's son Maximilien is in love with Valentine, Monte Cristo saves her by making it appear as though Héloïse's plan to poison Valentine has succeeded and that Valentine is dead. Villefort learns from Noirtier that Héloïse is the real murderer and confronts her, giving her the choice of a public execution or committing suicide by her own poison.
Fleeing after Caderousse's letter exposes him, Andrea gets as far as Compiègne before he is arrested and brought back to Paris, where he is prosecuted by Villefort. Andrea reveals that he is Villefort's son and was rescued after Villefort buried him alive. Villefort admits his guilt and flees the court. He rushes home to stop his wife's suicide but he is too late; she has poisoned her son as well. Dantès confronts Villefort, revealing his true identity, but this, combined with the shock of the trial's revelations and the death of both his wife and son, drives Villefort insane. Dantès tries to resuscitate Édouard but fails, and despairs that his revenge has gone too far. It is only after he revisits his cell in the Château d'If that Dantès is reassured that his cause is just and his conscience is clear, that he can fulfill his plan while being able to forgive both his enemies and himself.
After the Count's manipulation of the bond market, Danglars is left with only is a destroyed reputation and five million francs he has been holding in deposit for hospitals. The Count demands this sum to fulfill their credit agreement, and Danglars embezzles the hospital fund. Abandoning his wife, Danglars flees to Italy with the Count's receipt, hoping to live in Vienna in anonymous prosperity. While leaving Rome, he is kidnapped by the Count's agent Luigi Vampa and is imprisoned the same way that Dantès was. Forced to pay exorbitant prices for food, Danglars eventually signs away all but 50,000 francs of the stolen five million (which Dantès anonymously returns to the hospitals). Nearly driven mad by his ordeal, Danglars finally repents his crimes. Dantès forgives Danglars and allows him to leave with his freedom and the money he has left.
Maximilien Morrel, believing Valentine to be dead, contemplates suicide after her funeral. Dantès reveals his true identity and explains that he rescued Morrel's father from bankruptcy, disgrace and suicide years earlier. He persuades Maximilien to delay his suicide for a month. On the island of Monte Cristo a month later, Dantès presents Valentine to Maximilien and reveals the true sequence of events. Having found peace, Dantès leaves for an unknown destination to find comfort and a new love with Haydée, who has declared her love for him.
