Debra Morgan had the saddest and most surprising death in Dexter, but a line of hers from season 3 already foreshadowed her demise. Deb was Dexter’s younger sister, known for being a strong-willed, cursing, loyal detective at Miami Metro Police Department. Up until the season 6 finale, she was unaware that her brother was a serial killer, as well as not being privy to the fact that her father helped guide his killing code. While she still loved her brother in the last two seasons, she struggled with the moral ramifications of keeping his lifestyle a secret and the nerve-wracking choices she had to make to keep them safe.
In season 8 of Dexter, Deb had gone through a hard patch where she quit being lieutenant after killing LaGuerta to save her brother. She left Miami, started doing drugs and constantly drinking, and compromising her own investigations as she took a job as a private investigator. Dexter found her and brought her back to Miami, slowly bringing her back to becoming herself again. In the controversial final few episodes, when all seemed right with Deb coming back as a detective and finally admitting her love for Joey Quinn, she was shot after Dexter didn’t murder the hunted serial killer himself, ending up brain dead on life support after a subsequent stroke.
In the season 3 episode, "Easy as Pie," the Morgans’ family friend Camilla was in hospice dying, so Dexter and Deb went to visit her together. Deb couldn’t stand to be around it because sick people reminded her of her mom, eventually telling Dexter that if this were ever to happen to her, he should “shoot her.” She then makes sure he knows she’s not kidding, telling him that if it were him on life support, she would suffocate him or pull the plug so he didn’t suffer. The irony of this statement is that’s exactly how she would end up dying herself. After being brain dead with only a miracle to bring her back, Dexter decided to pull the plug on her life support and allow her to die just as she asked him to do years before.
Deb’s death was one of the top reasons Dexter’s original series finale faced so much controversy. Audiences didn’t believe Deb should die after all of the work she put back into herself in the final season, and fans especially disapproved of how Dexter disposed of her body. Miami was facing an immense storm that same day, which led Dexter to pull her life support, wrap her in a white sheet, take her on his boat, and dump her body in the ocean the same way he had all of his other victims. The death wasn’t justified enough to make sense for why Dexter’s strongest character after the protagonist himself would go so hastily.
Jennifer Carpenter has already been revealed to be returning in a cameo role for Dexter’s season 9 reboot “New Blood,” likely serving as the new Harry Morgan. Dexter will likely be wracked with guilt over turning off Deb’s life support, essentially being the hand to officially kill her, even though it’s what Deb already revealed she would have wanted. By bringing Debra Morgan back to the serial killer’s life, even if it’s just in his head or in flashbacks, Dexter is trying to amend where the original series went wrong with the character, and will hopefully give her a much better and rightful send-off.