The Count stays up the entire night, ruminating on his plan. He will fight the duel with Albert but allow Albert to kill him, thus preserving his honor while also doing what Mercedes asks—preserving the life of her son. That night he adds a codicil to his will, leaving large amounts of land to Haydee and his money at Monte Cristo to Maximilien Morrel. He then rides with Morrel to the dueling spot, where he meets Debray, Beauchamp, and, eventually, Albert in preparation for the duel.
In this way, the Count will not appear to have taken his own life, and will grant Albert the opportunity to prove his own honor in killing the Count. The Count also indicates that Haydee and Maximilien are to be his heirs. This is the first time in the novel he’s done this officially, although it’s been clear for some time that he considers Haydee and Maximilien to be like members of his family.
Albert, however, asks everyone to join together, and announces that there has been a change: he has learned that the Count is not only fighting the duel because of Albert’s provocation of the previous night, but also because of Fernand’s treachery of many years before, in which he stole Mercedes away from the Count. The Count can barely believe his ears, but he thanks Mercedes in his heart for telling Albert this ignoble fact about his father, thus saving the Count’s and Albert’s life and preventing the duel. The Count takes this as further affirmation of divine providence: that there is in fact a plan for him, that he is meant to be an “avenging angel” and to punish those who have wronged him, but not Albert, who is, in this grander scheme of the plot against Dantes, innocent of a crime.
Mercedes’ work, it turns out, was not done. In tipping off Albert to the fact that he would have been fighting a duel under false pretenses, Mercedes has managed to preserve the Count’s life and honor, and her son’s life and honor. Although there are not many moments in the text in which Mercedes is allowed to take center stage, this is one of them. Without her involvement, it’s clear that violence and death would have befallen at least one, and perhaps both, the proposed combatants in this duel. Her love for her son and for Dantes wins out over their misplaced desires for vengeance.