AN: After re-watching season 1 and catching an old episode of CSI, this idea crept into my head. I also vaguely stole an idea from an old 24 episode. Points if you can guess what it is. Set some time during season 1, maybe early season 2 of Fringe. "M" rating will kick in for the next chapter or two, because I know that's why you clicked on this fic in the first place. First chapter is the setup.

Enjoy. Reviews are love,

-Ari

Peter tapped his pen on the table, with his chin buried deep in the palm of his hand and his fingers doing their best to conceal the tension in his teeth. Without the support of his arm, his unhinged jaw might have dropped to the plastic tabletop with a shameless thud moments before. He was sitting in the most bizarre mission brief he had ever witnessed, and that thought alone was a whole other ironic hell.

Broyles had strung together three words that had no business cohorting in one conversation. Dunham. Brothel. Undercover.

These three words played on in an endless loop in Peter's head. His poor brain tried to make sense of them, to force them into a coherent thought, but his proverbial wheels just spun in muddy trenches. He stared at Broyles while he spoke, trying to rip some sense from this conversation and cram it into his thought process.

"Believe me when I say this, Agent Dunham. I did not want to authorize this," Broyles said, his face indecisive between disturbed and direct. "We're scraping the bottom of this god-forsaken barrel. We're running out of leads and time. We don't really have a choice. Because of the nature of the case, it falls into our jurisdiction."

Olivia sat with a furrowed brow; the fact that she didn't look like she'd been smacked headlong with a crow bar disturbed Peter.

"So, all of these career politicians dropping dead for the past three months with gaping sores all over their skin..."

"Have been traced back to this particular Vegas brothel," Broyles finished for her. "Walter turned in his analysis on the latest victim."

"Senator Beason? Walter said the sores all over his skin looked like genital warts," Olivia said evenly, although she looked like she was concealing a grimace.

Peter shuddered involuntarily, vowing to himself to invent a man-sized condom bodysuit for this trip. He would never have sex with strangers again.

"Correct. Since the senator was found in his home right outside of Boston, he has been the first victim Walter could examine within hours of his death, as you know," Broyles said. "Walter's rather unnecessarily detailed report outlines the pathology of the virus. It's like human papillomavirus on hormonally enhanced performance drugs. Anyone who contracts it will face almost certain death."

"So, we have a renegade pathologist using a venereal disease to assassinate politicians? How does he target them? How would he even infect them?" Olivia's brain was working just a furiously as Peter's, but she moving in a much more productive direction.

"According to Walter's report, our suspect managed to isolate a strand of the virus that only affects males. This particular brothel in Las Vegas caters to men who have a stripper fetish. We believe the suspect is somehow infecting the prostitutes, using them as carriers, and the clients contract the disease that way. Walter said the virus would only be contagious for 48 hours after contraction before it becomes dormant in a female. We believe our target has the resources to research the clientele, which men go in on which days and times and which girls they typically patronize."

"You think this is an inside job? The suspect works at the brothel?" Peter blurted out.

"We can't rule it out," Broyles said wearily. "You and Dunham will go undercover in this brothel, you as a patron and Dunham as an employee, so to speak."

Peter glanced at Olivia sideways, although her face was passive, he was sure he saw unadulterated terror in her green eyes.

"Dunham, I know this is asking a lot. But we're out of options," Broyles said.

They left the conference room, Peter with a tight chest and Olivia looking vaguely ill. After handing them a folder full of comprehensive documents on the case and flight tickets, Broyles had dismissed them with vague instructions to prepare for the trip. Over the next few days, Olivia's trepidation appeared to give way to her normal passive confidence. When Peter knocked on her apartment door a week later at 4 a.m. to leave for the airport, he might have even guessed that she was going on vacation if he didn't know any better. She cracked open the door, hand on a rolling suitcase, a duffel bag on her shoulder and wearing a sleepy smile.

"Hey," she rasped. Peter smiled at the lethargic husk in her voice.

"You ready to go?"

"Lead the way."

After loading up her suitcase, they set off for Logan International. Although their flight didn't leave until 7:15, Olivia had insisted on getting there before 5 a.m. so they could go over the case file and make it through security.

"Plus, the cafe in our terminal has the best bagels," she assured Peter.

She had traded her FBI black body armor for a nondescript, long-sleeve maroon shirt and sensible jeans that hugged her hips. Her hair was still vaguely damp; Peter could still smell her shampoo.

"I've been talking to Walter about his report," Peter said, reaching for a subject that knocked loose the urge to tuck her hanging strands behind her ear. "The virus almost acts like cancer on meth, the victims' organs just fail. He thinks the suspect is injecting the virus into the prostitutes, considering the profile is male and he can't be alive if he's infected."

"That makes sense," Olivia said, training her eyes on the road as Peter merged onto the ramp for I-90. "Police have reported finding track marks on the girls' inner thighs. According to Walter, it would be difficult to impossible for someone to inject themselves with drugs there without some serious consequences."

"I've also done some research on the brothel," Peter said. "It's called the Red Door, right off the strip on Sahara Avenue. According to the reviews, some pretty prominent figureheads have been spotted there. It's made up like a strip club, but it has stalls and rooms in the back for the X-rated activities."

"So, our suspect is a mad scientist with the wherewithal all to engineer a killer STD, and he's infecting prostitutes to take out his targets," Olivia's brow furrowed. "Broyles said he briefed the club owner, said the guy is protective of his employees and is being extremely cooperative. We're meeting him at 3 p.m. Our plane lands just after noon, so that gives us time to drop off our bags and grab something to eat."

Olivia yawned and stretched, her arms curling over the headrest. Peter tried not to look pathetic as he saw the thin fabric of her shirt stretch over her chest and flat torso.

"So, are you prepared to play your 'role'?" He asked slyly, his eyes holding the windshield up with determination.

"Yeah," Olivia laughed. "I even took some classes."

"What classes?" Peter felt his throat constrict as some unbidden images burst from the back of his brain. Olivia gave him a sarcastically reproving look.

"C'mon, Peter," She said, half smiling. "I'm pretty sure you can work that out for yourself."

After 30 more minutes of Olivia yawning and spewing case facts and Peter resolutely attempting to mentally deny his arousal at the thought of Olivia wearing barely anything and attached to a pole, they were dragging their bags through security. Two bagels and an hour of superficial conversation later, they were sitting on the plane. Olivia had fallen asleep, her head had slid onto Peter's shoulder. He guessed that she hadn't been sleeping much since that mission brief with Broyles a week ago. He couldn't really blame her; the stakes for this one were exceedingly high. If they were discovered or something went wrong, they were dealing with a seriously demented individual, someone who could kill quietly and passively.

After a long layover in Atlanta, the couple touched ground at McCarran International. Peter almost belly-laughed when Olivia told the car rental receptionist they were in Vegas to elope.

"Why are you smirking at me?" She asked as she drove off the lot to their hotel.

"Olivia Dunham, I could never picture you running off to Vegas to marry anybody," he laughed.

"Well, why else would you be in Vegas?" She asked indignantly.

"Oh, I dunno," he said, still suppressing a leftover chuckle. "Going undercover to bust badass pathological geniuses?"

"Shut up, Bishop," she said as she shoved her foot on the gas.

After they arrived at their Strip-adjacent hotel, Olivia checked them in before hoisting their bags up to their adjoining rooms on the 12th floor.

"Here's your key," she said, stopping in front of her own room. "I'll meet you out here in ten minutes."

Peter deposited his bags on the queen bed in his own room. He tested the mattress and changed his shirt before knocking on Olivia's door minutes later to let her know that he was ready to go. She opened the door with one hand, the other lost in the process of tying her hair in an atypically messy bun.

"Sorry, I was just getting cleaned up," she said, sounding out of breath and wearing a different, short-sleeve blue shirt. She left the door open for him as she finished her hair in an untidy loop and headed back towards her open duffel bag on her bed.

"No problem," he said, catching a glance of black lace as Olivia stuffed it bluntly into the bag before zipping it roughly and slinging it over her shoulder.

The left side of Peter's brain began screaming at the right. Peter felt a renegade train of forbidden images crash into his consciousness, images of Olivia strutting with a commanding stride in sky-scraping heels, covered in scraps of black fabric not modest enough to call itself clothing. The responsible part of Peter's mind tried to fetter the obdurate id ravaging his concentration to the boundary beyond conscience. This would be a dangerous undertaking for Olivia, he told himself. The stakes were immeasurably high.

But, holy shit, to see her shake it in black lace. An amygdaloid monster screamed in primal satisfaction from the bottom of Peter's brain. As she walked past him with an innocent smile, unknowing that she was literally undoing him with every little hint of vulnerability and unintentional sensuality, unaware of his lurch of arousal when she grazed his arm with her fingers, he wished he'd had time for a cold shower.