After changing their last name to Morcerf, Mercedes and Fernand lived a life of luxury and wealth, even moving to Paris and having a son named Albert later. But despite her new life, Mercedes felt sad and unsatistified.
She still carries out her strong feelings for Edmond Dantes. When she finds out The Count Of Monte Cristo is Edmond Dantes, she tries to convince him to love her once again, as Edmond Dantes. Even though the Count refuses to have her still think of him as Edmond Dantes (even though he knows he is still Edmond Dantes), Mercedes still loves him more than he thinks.
When Mercedes finds out Mondego was responsible for framing Edmond/the Count 25 years ago, she says her farewell to Mondego, unable to continue to bear his lies and deception, but is shot by him. Though she is able to survive, she is bedridden. When the Count/Edmond dies, she is seen crying in her sleep after being shot by Fernand, sensing that her love was passing on.
Five years after the events of the series, Mercedes moves back to her childhood hometown and is seen standing in front of The Count Of Monte Cristo/Edmond Dantes' and Count de Morcef/Fernand Mondego's graves in Marseilles.