A/N: This was co-written with asteraceaeblue and beta'd by allthebellsinvenice for the Sherlolly Big Bang Challenge started on tumblr and uploaded to AO3 (thank you, artbylexie!). It's posted in full on AO3 and I will upload two chapters a day here. Warnings for sex and violence. Enjoy!

Prologue: Dawn of the Dead

(Two months after Sherlock's 4-minute exile)

The smell of disinfectant and plastic overwhelmed Peter Welmsley from the moment he stepped into the room. He'd never been terribly comfortable with these sorts of visits, and this was his third in as many weeks. There was always too much white, too much fluorescent light and the vague smell of alcohol and something burning. It made him edgy, reminding him of doctors' offices and sickness. As an inspector for the British government, however, he had little choice but to go where he was pointed and report on the progress of their facilities.

If he was being honest, Welmsley found the inside of the building far preferable to the city outside (if it could be called a city). There was no order, no propriety. Traffic laws were nonexistent and he could not decipher if the people shouting at him as he walked by were trying to sell him cheap souvenirs or begging for (demanding, really) money. He'd never got the hang of Mandarin. Or was it Cantonese? No matter, his guides spoke English and that was all that mattered.

"So as you can see, Mr. Welmsley, the tests are all running according to plan and we are making great progress," his guide said as he gestured to the various workers sitting at lab benches and performing tasks he didn't understand.

"Yes, well," he sniffed, his nose stinging slightly. "Very good. And the prognosis? How soon can I expect to let my superiors know that we have something to sell to the public?"

"We are hopeful that we can deliver a successful product within the month."

Peter turned and saw the lead scientist on the project, one Doctor Nicholas Boehm. Tall and angular, he cut a perfect figure in his blue lab coat and dark trousers, his black-rimmed glasses perched atop his patrician nose. Blond hair flecked with grey gave away his age, though he looked a good ten years younger than he was.

"Doctor Boehm," Peter said, holding out his hand in greeting.

"Mr. Welmsley, always a pleasure," the other gentleman said, smiling as he shook his hand. "There's no need to subject you to any more of this – " He gestured to the lab. "What say we move on to a cup of tea in my office?"

"Delighted," Peter said with relief.

They hadn't gone far in the hallway outside the lab before they were approached by a woman in a white coat, a clipboard held firmly in her hands. She looked to be in her early 40s with shoulder-length brown hair. Pretty enough, he supposed, if you went for the older sorts. Blithely ignoring the fact that he was well beyond the mid-point of that same decade, he waited with ill-concealed impatience while she spoke to her superior.

"Doctor Boehm, we need your authorization to order more specimens," she said crisply, holding out the clipboard. "We lost another dozen in the last round of trials."

Boehm took in a thoughtful breath as he glanced at the paper. "Very good, Stapleton," he said, signing off on the form quickly. He handed the clipboard back to her. "Make sure to note the length of prodromal and acute periods, will you?"

"Yes, sir," Stapleton replied, turning and disappearing down the hall, quickly forgotten by Welmsley as Boehm escorted him into his office.

The good Doctor Boehm could make a proper cup of tea, that was certain, and the moment the steaming liquid entered Welmsley's mouth he felt right for the first time since his plane landed the day before.

"I won't bore you with the details of our recent research," Doctor Boehm said, leaning back in his office chair. "We can provide you with all of the paperwork to take back for your superiors to look at. What I can share with you is the genuine confidence that our days of dealing with this disease as we know it are almost over."

Welmsley shook his head slightly as he took another sip of tea. "Still don't fully understand the effort," he said. "Haven't seen it in England in years, you know."

"Ah, but imagine the security of knowing that no one will ever worry about it again, not even the threat of a foreign case slipping into the country," Boehm elaborated, resting his elbows on the chair arms and folding his hands over his stomach. "It will be the last thing on anyone's mind."

Welmsley raised his eyebrows and tipped his head, acquiescing to the superior knowledge of those in charge.

It all seemed to be in order by the time he had boarded the small commuter plane to Beijing two days later. The documents on the project were securely in his briefcase and he was happy to be on his way home. He complained to the steward that the cabin seemed to be rather too stuffy and he was sure that the air vent above his seat was not working properly. The steward apologized for his discomfort and said they would attempt to fix the air. By the time his flight from Beijing to Brussels landed for the hours-long layover, he felt the beginnings of a travel-induced cold, sniffling and coughing as he sought out some Nurofen and hoping the symptoms wouldn't be long lasting.

He simply went to bed when he reached his home, telling his wife that he would be calling out of work the next day. When his fever reached 35 degrees Centigrade and the chills made him shake almost non-stop, his wife insisted he visit the hospital.

He snapped at her, telling her it was just the flu and that the doctors never did anything but poke and prod him before telling him to get plenty of rest and drink fluids, and she would be more useful if she made him soup. Stupid woman.

During the night he woke, suddenly feeling full of energy and an aching, desperate need to get out. He was barely aware of how he managed to find his way to Soho, but he pressed his way into nightclubs and bars, handling his drink better than he'd ever managed to before. He questioned why he'd never taken advantage of places such as those before – they had the most beautiful women who smelled like vitality and sex and they were far easier to coax into the back of his car than his wife had ever been.

He lost track of the hours, lost track of the women, but he'd never felt more alive or full of vigor.

He didn't remember falling to the floor and passing out on the way to the loo in a pub, but he woke up in a hospital bed, hooked up to an IV and all manner of machines. The last thing he was able to register was attempting to rip the lines from his arms and shouting obscenities at the hospital staff as they fought him down to the bed.