When Walter examines the early victims, he says the bite marks are definitely human. But in attack mode, Mrs. Boone's teeth are anything but human-looking.
If you insert a needle into a person's spinal cord at the cervical (neck) section that would render the person tetraplegic. The antidote should have been injected at the lumbar area.
The second dead man picture Olivia showed Dr. Nicholas Boone during his interrogation, after his capture, is from a dead victim she only discovered way later in the episode.
Trivia: The news broadcast at the beginning has a text crawl stating "Mysterious fire breaks out downtown." This is a clue toward the next episode, "The Road Not Taken."
Trivia: The glyph for this episode is EIGHT.
Trivia: The Observer can be seen twice in the bar behind Bob Dunn; just before he tries to pick up the blonde girl at the bar and then again as he turns and sees Valerie.
Walter: (examining a corpse) You know what this reminds me of, Peter?
Peter: Nope, but I'm gonna guess it's something unbelievably disgusting.
Walter: Shrimp cocktail. You see, the shrimp must be deveined by putting a shallow cut down the back to expose the vein. Which in fact, is not a vein at all, but the crustacean's intestinal track.
Peter: Great, thanks for that. Another foodstuff I can cross off the menu for life.
Peter: Hey, are you okay?
Peter: Well, you were awfully quiet on the car ride over here and you just don't seem your normal, chipper self at a bloody, gruesome crime scene.
Olivia: Oh, I'm sorry, I'm, umm... it's home stuff.
Peter: Well, I know from home stuff. I live with a guy inspecting a severed spine.
Peter: You're suggesting that someone chewed his spine out?
Walter: Yes. But with a jaw strength well in excess of that of a normal human being.
Peter: Great. Well, maybe we're looking for Dracula.
Walter: Ha ha! Finally, son; you're opening your mind to new possibilities. But no, there are no vampires, sadly. But it'll be something exciting, I'm sure.
Walter: The C-1 cervical vertebra is connected to the C-2 cervical vertebra. The C-2 cervical vertebra is attached to the C-3...
Peter: That... Walter, that's enough.
Astrid: When you finally meet a nice girl, I would avoid bringing her home for as long as possible.
Astrid: The killer took the victim's spinal fluid? Why would they do that?
Walter: Where would the fun be if we already knew all there is to know?
Walter: Benzyl alcohol. A colorless liquid used as a bacteriostatic in solution for injection, topically as a local anesthetic. Personally, I like to use it as a mouthwash.
Walter: I am forming a hypothesis. Would you care to hear?
Peter: Well, I don't know. Would I ever be able to sleep at night again?
Walter: Well, that depends.
Peter: Depends on what?
Walter: On whether the light is on or not.
Peter: Do you really think it's a good idea to let him have free rein in Walter's Believe It or Not Emporium?
Peter: Everything stolen is not necessarily lost.
Olivia: Meaning what?
Peter: Meaning, if there's a car found stripped in the Greater Boston Area, I can guarantee you my man Mako has his big toe in it.
Olivia: You have a friend who runs a chop shop?
Peter: You make that sound so illegal.
Peter: You know what I hate worse than the cold?
Peter: Not much.
Club Girl: Now you're my kind of guy. What is that?
Peter: A handheld thermal radiometer. It tells me if you're hot.
Club Girl: So...
Peter: So you're definitely hot. But, I'm looking for someone with syphilis.
Club Girl: Uh, okay.
UK: May 10, 2009 on Sky1
Norway: May 24, 2009, on TVN
Finland: June 1, 2009 on MTV3
Germany: July 27, 2009 on ProSieben
Belgium: July 30, 2009 on RTBF2
Sweden: July 30, 2009 on Kanal 5
Latin America: August 11, 2009 on WB
France: August 12, 2009 on TF1
Poland: January 21, 2010 on TVN
Slovakia: February 14, 2010 on Markiza
Czech Republic: April 9, 2010 on Nova Cinema
Music: Bela Lugosi's Dead (Bauhaus), Tear You Apart (She Wants Revenge), Closer to You (Daniel Ash), Candy Darling (Daniel Ash), Discipline (Nine Inch Nails), Burning Up (Ladytron), Once You Say (Nitzer Ebb)
Blair Brown is credited but doesn't appear.