|First Seen||"Sean McNamara"|
|Last Seen||"Quentin Costa"|
|Played By||Bruno Campos|
Quentin Costa is introduced in the episode "Sean McNamara" as a plastic surgeon from Atlanta, Georgia. He is brought in to assist Christian Troy in fixing Sean McNamara's face (a slash to the right side of his face) after an attack by The Carver, a masked serial rapist preying on women who would ultimately become Sean and Christian's patients.
In the third season, Sean offers Quentin a limited partnership after Christian neglects to return to work after being attacked by the Carver. Initially, Christian refuses to accept having Quentin as an associate, but later changes his mind and supports the decision. A couple of episodes later, he and Sean go to a frat party together. They end up receiving fellatio from two college girls, during which Costa winks at Sean. This bothers Sean and he leaves the room. In the same episode Christian asks Costa to help take Kit McGraw off his hands because he is tired of the three-way relationship with her and Kimber Henry. While in bed with Kit on one side and Christian and Kimber on the other he reaches over and touches Christian's buttocks. Costa later explains that he is bisexual, and assumed Christian was as well. After Sean briefly leaves the practice, Costa remains to assist Christian with surgeries. Later Christian believes that Costa is on drugs and calls Sean to assist with the facial transplant surgery they are working on. Sean later returns to the practice.
Following Sean's return to the practice, both Costa and Sean admit their hatred for each other after the former enters a relationship with Sean's ex-wife Julia. After catching Costa having sex with a married male patient (a corporal), Sean blackmails him in an attempt to force him to quit the practice. Costa allows McNamara/Troy to buy out the rest of his contract at half price, only to then reveal he is staying in Miami to become the resident plastic surgeon at De La Mer, under the employment of Julia McNamara. He is later fired after an argument with Julia.
When Julia discovers she is pregnant, Sean and Christian suspect that Costa is the father. This was later proven false, as Costa (never knowing Julia was pregnant) admits to Christian that they never had sex. The child is now assumed to be Sean's.
At the end of episode 3.14 ("Cherry Peck"), it is revealed that Costa does not have a penis. Early in the next episode he attributes this to a genetic disorder known as 5-alpha-reductase deficiency that he suffers as a product of incest.
The third season's finale (Episode 3.15, "Quentin Costa") reveals Quentin Costa to be The Carver, with assistance from Kit McGraw, who is in fact his sister. This episode also explains that Kit and Quentin's parents were siblings and points to this as a possible explanation for their birth defects. At the climax of the episode, Kit apparently kills Quentin, but it is ultimately revealed that they faked his death so they could escape. They are last seen on a beach in Málaga, Spain, trolling for their next victim.