Deb's confirmation as the new Dark Passenger in the Dexter reboot signals big changes for Dexter's character. The announcement at this summer's TCA panel that Jennifer Carpenter would be returning as a spectral version of Deborah Morgan confirmed a long vaunted theory as she replaces Dexter's old Dark Passenger, Harry (James Remar). Dexter season 9 is set to be a direct continuation of the previous 8 seasons as an attempt to reverse criticism leveled at the series finale.
The Dark Passenger is the name Dexter gives to his urge to kill, which in later seasons fuses with the ideological version of his father that he has in his head. Harry imparted a strict moral code to a young Dexter, teaching him to channel his urges to kill into becoming a force for good in the Miami community.
Deb becoming Dexter's new Dark Passenger will inevitably change Dexter, and not for the better. Having Deborah in the driving seat will allow Dexter greater flexibility to enact his murderous whims, with no code in place to restrain him. The fact that the Dark Passenger Deb is a figment of Dexter's imagination will also make him more dangerous in the season 9 Dexter reboot.
The changing of the guard in Dexter's psyche will signal a radical shift in how Dexter views right and wrong. While Dexter at times flouted Harry's rules, particularly in season 8, his kills were mostly bound by "The Code", and Dexter ultimately did clean up the streets of Miami in a way the police department could not. In Dexter: New Blood, "The Code" looks to be all but dissolved, and the small town of Iron Lake, NY, will not have the plethora of distasteful characters Miami had. This means Dexter will likely kill characters across the new season who do not come close to fitting Harry's code. Furthermore, with the Dexter reboot trailer showing Deborah replacing Harry in Dexter's mind, it proves he has, whether consciously or not, chosen to dissolve the boundaries that previously held his murderous urges in check.
The more dangerous factor here is that Dexter has chosen to swap a pre-existing psychological construct for one that he has created. Whether through guilt, or a desire to change, Dexter is playing with fire by using his sister's memory as a support system. It is hard to imagine the Dark Passenger version of Deborah restraining Dexter in the same way his father's memory used to, especially considering how combustible Deb was when she was alive. Michael C Hall (Dexter) has already alluded to as much, stating during the TCA panel: "Harry was like Dexter’s north star in his consistent point of view, whereas Deb, in the context of this world, coming from everywhere. In that, she’s an internalized character for Dexter that represents just how far...he’s fallen— internally reeling and without a compass in a sense as much as he’d like to have one.” These changes to Dexter's character are clearly foreboding for both the actors involved in the project and the audiences waiting to see Dexter unleashed this season. In life, Deborah was a driving force for many of the good things in Dexter's world, but in death, she may prove the opposite for the characters of Dexter: New Blood.
Dexter: New Blood will debut on Showtime on Sunday, Nov. 7th at 9 p.m. ET.