Some time has passed since Lumen Pierce entered and shortly left Dexter Morgan's life, having moved on raising his son...new challenges await him as he struggles to satisfy the Dark Passenger within and deal with new faces in town, such as a mysterious artifact expert Travis Marshall and religious ex-con Brother Sam. In addition, his relationship with his own sister Debra Morgan will be put on the line as she may come closer to the truth...or forever remain in ignorance of his true nature.
Several actors have been revealed to guest star as recurring characters, including Colin Hanks, Mos Def (now referred to as Yasiin Bey) and Edward James Olmos. Olmos is set to play a brilliant university teacher of religious arts, while Mos will appear as an ex-convict turned minister who unfortunately cannot escape the life of crime that he left behind. Details about the character Colin Hanks will play have been kept under wraps, with some sources reporting that his character will be a student of archeology tied to a string of murders.
It has been stressed that this season will likely not have a major Big Bad, such as for every Season before it but rather any major villains will tie into the story effectively in a unique fashion. It is also intended for the relationship between Dexter Morgan and his sister Debra Morgan to reach new bounds, possibly finally revealing his secret to her (this is just speculation, and has not confirmed).
As more trailers and Behind the Scenes videos are released, the clear direction this season is heading in has become more clear. The season starts out with Dexter working to obtain some sort of ideal to pass onto his growing son Harrison, something that isn't his own Dark Passenger. Likely in dealing with target Joe Walker, he begins to question if religion is the system he wants to bring into his son's life and he starts asking friends about it (such as Batista), eventually encountering several religious characters such as Brother Sam and eventually Professor Gellar as well as his student Travis Marshall.
The antagonistic side of this season's story falls on a series of in-explainable murders placed on Miami's doorstep by a new serial killer. The man responsible is shown to be Professor Gellar with the aide of his pupil Travis Marshall, passing on a religious teaching that the killings being committed aren't bad and are in fact the right thing to do. It seems as if Gellar is on a similar wavelength with veteran serial killer Arthur Mitchell, likely having been responsible for murders long before the current season and is now attempting to pass something on in his way...just as Dexter is trying to pass onto his son.