Monte Cristo and the man acting as Andrea Cavalcanti visit the Danglars’s home. Eugénie escapes to her room to play music with her constant companion and music teacher, Louise d’Armilly. Danglars insists that Andrea be allowed to join in the two women’s music-making. Albert then arrives. Danglars is excessively rude to him.
On the way back to Monte Cristo’s house, Albert laughs over Danglars’s obvious preference for Andrea as a son-in-law. Albert then asks to meet Haydée. Monte Cristo assents to the meeting with the condition that Albert not mention the name of his father. Haydée tells Albert the tragic story of Haydée’s childhood. Her father, Ali Pacha, was the ruler of the Greek state of Yanina until a French soldier, who had become Ali Pacha’s right-hand man, surrendered Ali’s castle to the Turks and then betrayed him, allowing him to be brutally murdered by his enemies. This Frenchman then sold Haydée and her mother into slavery. Her mother died soon thereafter, and Haydée was eventually liberated when Monte Cristo purchased her freedom. Albert is bewildered by the story, not realizing that his father is the treacherous Frenchman who betrayed Ali.
Villefort receives an angry letter from Franz, calling off the engagement. Noirtier changes his will yet again, leaving all his fortune to Valentine on the condition that she is never separated from him. Meanwhile, Fernand pays a visit to Danglars in order to finalize the engagement between Albert and Eugénie. Much to his dismay, Danglars tells him that he has changed his mind about the engagement. Though Fernand presses him, Danglars refuses to divulge the cause for his change of mind.
The next morning a small article appears in Beauchamp’s newspaper, reporting that a man named Fernand betrayed Ali Pacha to the Turks. Though there are many people who bear the name Fernand, and no one thinks to associate this article with the Count de Morcerf, Albert is convinced that the article is a libelous slander against his father. Despite Monte Cristo’s pleas for Albert to show restraint, Albert orders Beauchamp to retract the article or else fight a duel. Beauchamp, who did not even write the offending article, asks for three weeks to investigate the matter before he is forced to decide between these two options.
Barrois fetches Maximilian on behalf of Noirtier. As Albert, Noirtier, and Valentine discuss plans for the future, Barrois, overcome with thirst, takes a drink from his master’s lemonade. Almost instantly, he falls sick and dies. The doctor discovers that there is brucine in the lemonade. Though Noirtier has drunk some of the lemonade, he is not affected because the small amount of brucine he takes every day for his paralysis has given him a tolerance for the substance.
The doctor deduces that the poison was almost certainly meant for Noirtier. He then concludes that Valentine must be the murderer, as she is the sole heiress of all the intended victims thus far.