This episode was originally intended to air second, which is why the relationship between Carl and Perri is somewhat tenser then in earlier episodes. As per the DVD extras, the scene with Alex in the morgue originally was written to establish his first meeting with Perri. The dialogue here was exchanged with the dialogue in "Three" when that episode was changed in air order to feature Alex's first appearance.

"Skorzeny Security" is an in-joke reference to Janos Skorzeny, the name of the vampire in the original 1972 Night Stalker movie.

Carl: (opening voiceover)I drive the night, looking into the darkness where our fears reside. Of things the mind dismisses, but the heart knows are real. Evils that lie hidden in the blackness. I have seen these evils. They have taken my wife, pregnant with a child never to be born, leaving me haunted by questions about her strange death and the deaths of so many others no one else dares to explain. So I drive, knowing we fear the night not because it hides these evils, but rather because it reveals them.

Perri: Do you ever use the front door?
Carl: Not if I can help it.

Jain: “In battling evil, excess is good.” It’s Kahlil Gibran.
Carl: Sounds more like Donald Rumsfeld.

Anthony: If this killer wants to drink water with his hands, why doesn’t he stick them under a faucet?

Carl: (closing voiceover) There are evils that live amongst us, hidden behind walls, lurking in dark shadows. Open your eyes and you’ll see them, but be careful you don’t open them too wide. For once you’ve seen the darkness, the fear of it remains a part of you.