'''Season 1, Episode 18''':
!Midnight

The Fringe team investigates the murder of Bob Dunn in his apartment. He is found with a severed spinal column, and his spinal fluid drained out. While autopsying the body, Walter discovers human teeth marks containing saliva with traces of an extinct strain of syphilis. The team discover that a lab sample of the strain was sold to Lubov Pharmaceutical, which also bought other samples of bacteria. Lubov has ties with ZFT. The investigation leads to the address of Nicholas Boone, the head of the company. Boone admits he works for the bioterrorist group ZFT, and will give them everything he knows on the organization if they will save his wife Valerie from them. After leading Olivia to a restaurant, a ZFT hideout, she finds no sign of her, and Boone admits that Valerie is the killer they are looking for; ZFT infected her with a contagion when Boone initially refused to cooperate. The contagion burns spinal fluid faster than her body can replace it. In a vain effort to work on a cure several weeks previous, Boone used some of his own spinal fluid, costing him the use of his legs. Over the course of the episode, two more male bodies are discovered, having died in a similar manner.

Boone is allowed to work with Walter in his laboratory on the cure, later finding out they have to make an augmented form of penicillin, however the first trial is unsuccessful. Boone realizes that more spinal fluid is needed to complete the process, and sacrifices more of his. Astrid finds a link between the three victims; they all visited the same nightclub. Olivia and Peter enter the club and manage to find Valerie, with the help of a thermal imaging camera, as her infection causes her to have an elevated body temperature, and subdue her with tranquilizer guns. They return to the lab where Valerie is successfully cured, but Boone dies from the loss of spinal fluid. However, Boone managed to leave a pre-recorded message for Olivia, informing her that ZFT has been funded by Massive Dynamic founder William Bell.

Meanwhile, Olivia's sister Rachel learns that her estranged husband is divorcing her and demanding full custody of daughter Ella, claiming that Rachel is an unfit parent. In response, Olivia asks Broyles for the phone number of his divorce lawyer.

!Tropes
* ActuallyPrettyFunny: After seeing that Walter has installed the clapper on the lab lights, Peter isn't annoyed at all, but merely smiles in amusement at his father's antics.
* ApologeticAttacker: Valerie apologies to at least one of her victims before killing him.
* TheAtoner: Nicholas Boone, for unwittingly helping ZFT.
* BirdsOfAFeather: Walter and Nicholas Boone quickly get along, both for the interest in science and their guilt over what their work has done.
* BusinessTripAdultery: Bob Dunn meets Valerie while out at a club looking for someone to hook up with while his girlfriend was the one out of town on business.
* CreepyBlueEyes: Valeria, as well as a dog and a mouse, infected with the mutagem.
* [[DeadManWriting Dead Man Taping]]: Since he is about to sacrifice himself, Nicholas leaves Olivia an tape telling what he knows of ZFT, namely that William Bell is behind it.
* EvilCripple: Subverted. Nicholas isn't evil at all.
* EvilIsBurningHot: Valerie, due to being infected with a mutant syphillis-vampire virus.
* GlamourFailure: When Valerie is attacking you, her eyes glow blue and she grows another set of sharp teeth.
* HappilyMarried: Nicholas and Valerie, pre-ZFT turning her into a vampire-esque mutant.
* HeroicSacrifice: Nicholas sacrifices himself to cure his wife. He also leaves a tape for Olivia accusing William Bell of being the man behind ZFT.
* HorrorHunger
* NeckSnap: Up To Eleven. Valerie kills her first target like that at least, and [[BodyHorror all victims have the back of their necks ripped open, separating skulls from spines(nearly decapitating them), exposing their spines like a lobster]].
* NoodleIncident: Walter has apparently cured super-pneumonia in the past with super-penicilin.
* NotHimself: Valerie's infection has completely changed her personality, to the point Nicholas can't help Olivia find her because she's completely unpredictable.
* TragicMonster: Valerie Boone. At least one scene has her crying, [[AndIMustScream implying at least some part of her is aware and regretful of what she's doing, but unable to stop]].
* TheVamp: How Valerie gets her food.
* TheWoobie: Nicholas and Valerie, all the way. And by the end, Nicholas dies, leaving Valerie alone.