Dexter: "The only way to kill a Dark Passenger is to take out the Driver." "The Dark Passenger" was a concept used within the DEXTER Universe that represented the "demon" inside of all of the Murderers that actively made them do terrible things. While it was actually being built upon as an entity in the novels, it was more or less (in the tv series) the level of "darkness" and instability in each person's personality that could either control them or be contained.