Fernand says that he would have killed Edmond on the spot if Mercédès hadn't threatened to kill herself in retaliation.
Danglars, who doesn't give a darn about Mercédès, wishes Fernand had just gotten it over with so that he, Danglars, could become captain. He decides something needs to be done in any case.
After getting Caderousse totally wasted (they don't want him interfering with their plan), Fernand and Danglars quickly get down to business and try to figure out a way to ruin Edmond's life. Caderousse warns them that Edmond will find some way to take revenge if that ever happens, but they ignore him.
Danglars quickly thinks up and executes a plan. He writes a letter (using his left hand, in order to disguise his handwriting) denouncing Edmond:
The crown prosecutor is advised, by a friend of the monarchy and the faith, that one Edmond Dantès, first mate of the Pharaon, arriving this morning from Smyrna after putting in at Naples and Porto Ferrajo, was entrusted by Murat with a letter for the usurper and by the usurper with a letter to the Bonapartist committee in Paris.
Proof of his guilt will be found when he is arrested, since the letter will be discovered either on his person, or at the house of his father, or in his cabin on board the Pharaon.
Danglars crumples up the letter and throws it into a corner – he wants to convince Caderousse that it's all a joke. Danglars then takes the drunken Caderousse and hurries him off toward Marseille.
Fernand grabs the paper and hustles down a side street, intent on delivering the denunciation.