Dexter Morgan kills people. He hunts and stalks his prey, abducts them to his meticulously prepared kill-room where he exacts his punishment upon them. But it is not only punishment: For Dexter, killing is an appetite he must quell at regular intervals. He must kill, must draw the final blood.
Some call him a vigilante—his antics are similar in some respects to superheroes who hunt down the bad guys and rid the world of their evil—but he does not kill for the sake of eradicating evil, rather to satisfy a deep and gnawing hunger.
So where is the Gospel here? There are several parts.
In Season One, Dexter, along with viewers, discovers his brutal past. When he was a toddler, his mother was abducted and murdered by drug lords with a chain saw; Dexter witnessed the entire episode. Several days later, police found him sitting in a pool of his mother’s blood. Though for many years he does not remember the incident, it engendered in him an inexorable obsession with blood and death.
Upon researching his past, discovering—and remembering—the incident, he understands that he was “born in blood.” The incident was a birth into his present nature, one of unquenchable bloodthirst. He refers to this appetite as his Dark Passenger.
Different people use different names for the appetites we discover within ourselves: Dexter calls it his Dark Passenger, and the church refers to it as original sin. We have all been born in blood; we all have appetites for indecorous activities that grow like weeds among our desire to do and be good. These weeds are our Dark Passengers.
We were simply born this way, born in blood. We were born with complete and good nature that has to fight against a Dark Passenger for light and breath. This is not something we choose; indeed, we call it human nature.