It is seemingly not possible for “Dexter,” as a franchise, to move forward. In the final moments of the sequel series “New Blood,” which aired eight years after the original series finale in 2013, Michael C. Hall’s serial killer was fatally shot. This development, on its surface, marked the end of the road for one of the defining leads of the antihero era, a role Hall had been playing for 15 years at the time. Sure, yet another follow-up, “Resurrection,” would pass the torch to Dexter’s son Harrison (Jack Alcott). But if network Showtime wanted to keep wringing drops from this blood-soaked towel,...