Chapter 1.

"221B Baker Street," commanded Sherlock as he pulled a car door closed behind him. The driver didn't respond, instead turning to Mycroft, who climbed into the front seat with a sigh.

"Sherlock," said Mycroft in a weary tone, "This is not one of those ubiquitous cabs you're so fond of gadding about London in. This is my car, and my driver, and we're not going anywhere until I say so."

"And we're not going to 221B in any event," John chimed in with a sharp look at Sherlock.

"Of course we are," he snapped back.

The driver pulled down his visor against the sun glinting off of the private jet parked next to the car and waited for instructions. His passengers had just departed the plane, which had landed mere minutes after takeoff. It had been bound for Eastern Europe with Sherlock aboard to complete a mission which, in Mycroft's inarguable estimation, would prove fatal to him in about 6 months.

The mission had been an alternative to lifelong residence in a prison cell for his murder of newspaper magnate Charles Augustus Magnussen. The latter had placed Mary Watson at risk by threatening exposure to her enemies. Apparently, those were legion, as Mary's past had involved more than a bit of assassination on behalf of the US Government then, eventually, certain high bidders. Magnussen's death was, to Sherlock's mind, a more than fair trade for Mary's freedom. More importantly, it ensured her continued association with her husband and Sherlock's best friend, John Watson. That would make John happy, and by extension, Sherlock.

Unfortunately, the Commonwealth didn't agree with his logic. It took a dim view of citizens meting out capital punishment to one another, so Sherlock was given a choice: solitary confinement away from prisoners whose presence in jail was his handiwork, or near certain death in far-away Serbia. He settled on the latter as being preferable to an eternity alone with his thoughts.

Even so, while Sherlock may have been willing to sacrifice himself to Queen and country in payment for murder, he wasn't enthusiastic about the prospect. Escape was an appealing alternative. None being to hand, however, he took the next best option, sinking into a drug-induced oblivion.

Not incidentally, being deeply high also brought clarity of thought to Sherlock's complicated brain, allowing him to explore his favorite mystery of whether and how James Moriarty, consulting criminal second only to Magnusson in evil intent, could have survived a gunshot which removed a sizable portion of his brain. Ingesting a potentially lethal cocktail of opiates, amphetamines and other drugs provided by his obliging fellow prisoners (many of whom were all too happy to make sure the poison reached him) offered Sherlock endless opportunity for such entertainment. And if he didn't manage to survive the cocktail's effects, well, someone else could surely take his place in Eastern Europe. It was a win-win.

Or would have been, had he not decided to take a massive dose not long before boarding his flight. The rapid return to the landing field didn't give the drugs time to leave his system. Indeed, as the wheels touched down, he had never been higher. So it was that his brother, best friend and the latter's wife found him incoherent and nearly unconscious in his seat. On the upside, he now had a clear vision of Moriarty's post-mortem plans. On the downside, his drug use was certainly going to be a lively and unwelcome topic of conversation for some time to come.

"No," said John firmly.

"No, what?" huffed Sherlock.

"No, we're not going to Baker Street. God knows what kind of crap you have crammed into every nook and cranny there. Besides, you're going to come down hard and you're not doing it alone. We're going to our house," he glanced at Mary for confirmation. She nodded.

"Ridiculous," Sherlock responded.

"Mycroft," John said pleadingly.

"Yes, Sherlock, I'm afraid that I agree with John on this. You forget that I've had the unpleasant experience of watching you recover from a near overdose. It is not an experience I wish to repeat, nor is it one you can handle on your own. We'll do as John suggests." Mycroft's tone left no room for argument. Sherlock gave him one anyway.

"I. Am. Fine," he growled. "I don't need a babysitter-" Just then, his body betrayed him with a series of severe muscle twitches. Sweat broke out on Sherlock's brow. He stiffened, fighting for control over his autonomic nervous system. "We do not have time for this. I know what Moriarty has in the works and—"

"Shut up," John said, his voice quiet but ringing. "Just shut up. You think I don't know what's going on here?" Sherlock looked at him questioningly.

"Six months, Mycroft says." John's voice took on a fake baritone in a cruel imitation of Sherlock's own. "He's never wrong, you said. What you didn't say was that you weren't coming back—you didn't have six months to work, you had only six months to live! So this," John waved over Sherlock's form, which continued to twitch and sweat. "This was you not caring. Not about whether you lived or died, and not about how we'd feel when you were gone. Again." John breathing was now as nearly as labored as Sherlock's. "Wasn't it?"

Sherlock didn't reply.

"WASN'T IT?" John roared. Mycroft flinched and Mary reached for John's arm.

"Look, Sherlock, you know we appreciate…we can never repay…what you did with Magnussen…" John was suddenly at a loss for words. The wind seemed to go from his sails.

"Just, I can't lose you again, okay?" Sherlock looked away to study his hands. "So let me do this. Take care of you this time."

Silence filled the car. Sherlock sagged, then raised red-rimmed eyes to John.

"I want to go home, John." His voice held a whisper of vulnerability.

"Right," said John. "So we go to Baker Street. But I'll—" Mary squeezed his arm. "We'll stay with you through this, yeah?"

Sherlock nodded. Mycroft let out a breath he hadn't quite realized he was holding.

"221B Baker Street," he said. The driver came to attention and drove the now quiet car away.

Sherlock's recovery from his chemical dalliance was every bit as gruesome as Mycroft had implied it would be. Migraine, nausea, respiratory distress, hypercapnia, muscle spasms, profuse sweating—all would be his constant companions over the next 48 hours. Only John and Mary's presence kept him from seeking relief from just one more dose, then another and another. And only their medical expertise allowed them distance from the horror of watching their friend disintegrate before their eyes.

"Moriarty," groaned Sherlock, who was slumped before his toilet. Gulping back another round of retching, he waved a hand toward John. "He set it all in motion. Knew he was going to die—wanted to die—so he set it up before…" Sherlock broke off as another wave of nausea caught him.

"Sherlock, now's not the time," John interrupted.

"It IS," insisted Sherlock. He leaned back against the bathroom wall with a deep breath, wiping his mouth. "It has to be. What Moriarty has planned is vast and could take effect at any time. It has a life of its own, John, a virtual existence. Any place can be its home, anything its host. It…" Sherlock broke off despite himself, lost in a series of spasms which shook his limbs.

Deciding that a distracted Sherlock was better than one in pain, John interjected. "What is 'it', Sherlock? Biowarfare? Is there an epidemic coming, a mass infection?"

"Yes, and no," said Sherlock, once he'd caught his breath. "I don't know exactly what is coming but it will be big and we must stop it. The risks are too great."

"Risk?" asked John. "Risk to what?"

Sherlock straightened. Eyes glittering in excitement (and not a small amount of fever), he smiled.

"Life as we know it."