Throughout the second season, Debra stays in her brother's apartment as she deals with the trauma of what happened, but leaves his apartment in a mess. Debra is a key member of the police task force in charge of finding the Bay Harbor Butcher, who is secretly Dexter. She falls for an older man, Frank Lundy, the FBI agent in charge of the case, all the while improving her ability on the job. By the end of Season 2, Debra has recovered from the trauma of the Ice Truck Killer, confident as an officer, and is determined to get her detective shield.
In Season 3, Debra has had her hair cut to shoulder length, has "sworn off men, liquor and smokes" and is even more determined to get her silver detective shield. She is working with a new partner, Detective Quinn, but has been approached by an Internal Affairs officer who tells her that her partner is being investigated as a dirty cop, but she refuses to help them. She was originally part of the team investigating the murder of Miguel Prado's brother, Oscar, but because of her lack of tact and people skills she was removed from the case by newly promoted Angel Batista; however, the case she had been assigned (the murder of a young woman) was eventually found to have been connected to the Skinner case, which she solved with the help of Anton, a C.I. whom she started dating after saving his life from the Skinner. Because of her success on the Skinner case, she was promoted to detective at the end of the season.
She is known to have a very foul mouth, and she hardly speaks a sentence without swearing. This has nearly gotten her into trouble, as she often speaks profanely to her superiors, only to realize a few seconds after. It finally got her into trouble in the third season, as a poorly-timed public comment caused her to be kicked off the Freebo case. She is also known for being easily angered and frustrated by suspects. Though she is frustrated at Dexter's inability to open up to her, she has defended him on more than one occasion.
A conversation between her and Dexter leads to her finding out that her father slept with one of his confidential informants. She investigates the files on Harry's informants and interviews some of them, hoping to find the one with whom Harry had an affair. One of the files is shown to be that of Laura Moser. Also during this time, her relationship with Anton had been breaking, especially now that he had secured a gig in the city instead of on a cruise ship. Also, Frank Lundy returns to Miami to hunt the Trinity Killer, and Debra once again becomes involved with Lundy. Soon, both she and Lundy are shot by an unknown assailant suspected to be the Vacation Killers. In her hospital bed, she confesses to Anton that she slept with Lundy, prompting him to leave her. Lundy dies, and she eventually concludes that the Trinity Killer must have been the shooter. As a result, Debra opens an investigation on the Trinity Killer. However, it is later determined that Trinity could not have been the shooter, since her wounds from the bullet were at a horizontal line, therefore someone of Masuka's height had to be the shooter. During a Thanksgiving dinner Debra remembers a conversation she had with Christine Hill and realizes Hill has knowledge of the shooting that no one outside the police department should possess. This leads Debra to believe that she was the shooter. This is backed up later when it is revealed that Hill is the daughter of Trinity. Hill later confesses to Debra that she was the shooter, and proceeds to shoot herself in the head. Due to her solving the Lundy killing, Debra restarts her search for Harry's C.I. mistress, and finds out about Laura Moser, and the fact that Dexter and the Ice Truck Killer were brothers.
