Season five In season five, Quinn comes to suspect that Dexter murdered his wife Rita Bennett (Julie Benz) after learning that Rita shared a kiss with a neighbor, mixed with subtle differences in the modus operandi of the supposed killer, Arthur Mitchell (John Lithgow). Following the fact that Dexter was part of the raid during Rita's time of death, he begins to focus on the composite sketches of "Kyle Butler" and determines it to be Dexter. After tracking down Mitchell's son Jonah (Brando Eaton), who was due to enter witness protection, he attempts to have him identify Dexter as Butler, but is caught by marshals and suspended. Unable to continue, Quinn hires private investigator Stan Liddy (Peter Weller) to investigate Dexter. After a one-night stand with Debra, Quinn repeatedly tries to get her back into bed, eventually succeeding. The two begin to date, until Debra discovers that Quinn was suspended by LaGuerta for investigating Dexter. In order to show her that his feelings for her are real, Quinn tells Liddy to drop his investigation of Dexter. Liddy delivers to Quinn pictures of Dexter and Lumen Pierce (Julia Stiles) disposing of a body. When Liddy is murdered, Quinn becomes a suspect because of the five phone calls Liddy placed to him directly prior to his death, as well as the blood on Quinn's boot. Dexter, who killed Liddy to protect himself and Lumen, fakes the blood report so Quinn will be eliminated as a suspect. Quinn goes to Dexter's son Harrison's birthday party with Debra, and thanks Dexter for his help. Season six At the start of season six, Quinn and Debra have been living together for a few months. Quinn proposes to Debra, but she turns him down because she wants their relationship to stay as it is. As a result, they break up. With Debra's concurrent promotion to Lieutenant, Quinn begins to resent her, believing she values her work more than she does him. He begins drinking heavily and having random one-night stands, once turning up to Debra's housewarming with a girl he flippantly refers to as "chick from bar", and hitting on Batista's sister Jamie (Aimee Garcia). His womanizing also affects his work when he endangers the investigation of suspected "Doomsday Killer" Professor Gellar (Edward James Olmos) by sleeping with his assistant, an important material witness. Debra calls him into her office to tell him they can never