*spoilers*
Dr. Jennifer Melfi is one of the very few characters on the HBO television show, The Sopranos, who isn’t in some way associated with the mob. Her character is introduced in the first episode, in which she seeks to treat Tony Soprano, at that time a captain in the New Jersey mafia, for his anxiety attacks. Her character’s arc over the course of the show is her encounter with the evil perpetrated by Tony Soprano and her realization that her methods in psychology can have no effect on a murderous sociopath.
In the first season, we see Jennifer impressed and even to some extent attracted to Tony Soprano. She actively defends him to her ex-husband, who sees Tony as an instance of people doing damage to the reputation of Italian Americans. However, as the show continues, she becomes increasingly suspicious of him, realizing that many of the people he speaks about end of dead.
What she never really realises is that Tony is actually using her to become a better criminal. In one scene, we will see Tony have some sort of breakthrough in therapy and then, in the next scene, he will apply that breakthrough so as to kill someone. For example, Jennifer helps Tony overcome his guilt with respect to Tony Blundetto, which makes it easier for Tony to kill him.
Dr. Melfi also finds herself actually using Tony herself at one point for her own needs. Early in the third season, she is sexually assaulted and the perpetrator is released on a technicality. She realizes that if she said something to Tony, he would have the perpetrator killed, and she is greatly tempted to tell him. Although she doesn’t tell him, the very fact that she could tell him makes her feel more powerful.
Ultimately, though, Melfi realizes that the darkness of Tony is simply too much. Two things turn her against him. First, he tries to seduce her at the beginning of Season Five. When turned down, he becomes angry and insulting. Second, she figures out that he killed Adriana. While this is never said explicitly, look at her face when Tony mentions how he helped Christopher handle a problem “of his own making.” By the sixth season, she despises Tony, and her interactions become increasingly hostile to the point where she drops him as a patient.
