This is a prequel to Carpe Diem. I highly recommend you read it first. The title will be explained at the end.
Sherlock hadn't always been without warning before a seizure. When he was younger, around the time he was still having anywhere from zero to ten a day, he would be able to tell when they were coming.
Other people, the doctors and his parents included, called it an aura. Sherlock hated that. They should just call it what it was- a simple partial seizure. Thankfully, Mycroft agreed with Sherlock. He was the only one who did. The simple partial seizure was often followed by a complex partial seizure, which was always followed by a tonic-clonic seizure.
Although they were rather annoying, they were useful, allowing Sherlock to find somewhere to lie down instead of just collapsing as the seizure began, often hitting his head on something and sometimes getting cuts that required stitches. He favoured his room; he had a large bed that was soft and safe and private. Sherlock may only have been a young child, but he was rather advanced for his age, as anyone who met him soon learned. He didn't enjoy being gawked at as he flailed and twitched on the floor, contorting into strange positions and making horrifying sounds, occasionally wetting himself.
No, Sherlock could most certainly do without that.
Except Mycroft frowned upon that. Because every time he entered Sherlock's room to find him sleeping off a seizure, or entered while he was in the midst of one because he'd heard the noises, he was absolutely furious. But this was Mycroft Holmes, future British government, and he would not have gotten there if he didn't know how to control his emotions.
So he smoothed down Sherlock's hair and whispered to him as he woke up, exhausted and confused, getting him clean clothes and reassuring him it wasn't his fault, and saved that anger for later when he could properly scold Sherlock for trying to deal with this on his own.
Oh, and he did. Because he quietly raged at Sherlock enough times that he actually listened, letting Mycroft know before he had a seizure, allowing him to come sit with him, just in case. And of course he acted all insulted, like it was an invasion of his privacy, but the Holmes brothers could read each other like books, at least at that time, and Mycroft knew that it was all a show. Because it was always nice to know someone would always be there when you woke up from the nightmare, someone to whisper in your ear that you were safe, and could rest, because they would fight off the monsters.
But nothing ever stays the same, and Mycroft grew older and went off to school, leaving Sherlock at home with two parents who didn't get it and a school that was full of cruel and immature children. Because between Sherlock's habit of revealing everything that everyone was hiding and his propensity to fall down with little warning and twitch around on the floor, he was not the most popular person.
So Sherlock mostly hid in the library, reading books, and there was even a beanbag that mysteriously appeared there a few weeks after Sherlock had his first seizure in the library. The librarian, a lovely woman, unable to have children but loved them (explaining why she worked in a school) denied Sherlock's accusations that she brought it in just for him, but they both knew. So Sherlock helped her fix the cataloguing system and suggested books to get, and she made sure he was safe and that no one ever made fun of him in her library.
The simple partial seizures were really the only thing that was keeping him from looking entirely stupid, forced to wear a helmet all the time, in case he suddenly fell down, which Sherlock never would have done. He'd rather have been at A&E every other day to get cuts stitched up than have to wear a helmet that essentially labelled him as defective. People figured it out soon enough, there was no need to advertise it.
When Sherlock was a teenager, they finally got the right combination of meds that reduced the seizures to once or twice a week, instead of the usual same in a day. Sherlock practically felt free, but his parents didn't see it that way. So Sherlock wrote to Mycroft, begging him to help convince their parents that he could most definitely go out on his own and could learn to drive, because he always had a warning before he seized. But it took Mycroft ages to write back, and when he did, it was stiff and formal, informing Sherlock that their parents were indeed right, that he still couldn't drive and needed to be looked after like a small child.
Sherlock burned the letter as soon as he finished reading it, but there was no burning it out of his mind.
So he'd leave the house and do experiments until all hours in the tree house he and Mycroft had built when they were younger, complete with a boardwalk for when Sherlock was still in his pirate phase. He'd stay there for hours, sleeping off the after effects of a night complicated by blurry vision and the scent of coffee, cursing his damn screwed up brain for ruining perfectly good experiments that were time sensitive.
His parents died when he was sixteen, Father rather unexpectedly, which was probably what pushed Mother over the edge, seeing as how she'd been slowly getting there for years now, constantly fighting a war she could never win.
Mycroft was made his legal guardian.
Sherlock counted down the seconds until he turned eighteen, knowing all the while that even that wouldn't get rid of Mycroft. Because his damn big brother was Big Brother, controlling CCTV cameras as a trick on first dates that never progressed to seconds, mysterious black cars pulling up beside Sherlock on the street and whisking him away when Mycroft wanted to speak with him.
But he could try.
And he sure gave it a damn good effort.
He went to school for a while, taking chemistry, but soon grew tired of that kind of chemistry and dropped out. He moved onto a different kind of chemistry and six months of his life practically flew by on silver wings until he fell, and fell hard, waking up in a hospital bed with Mycroft glaring at him, going on and on about how he'd been in status for almost fifteen minutes, his heart stopping once and his breathing twice.
So Sherlock cleaned up his act, but it sucked and it was hard and most of all it hurt. But he did it because he didn't want to risk the brain cells and besides, he found something even more addicting. The Work.
The Work that had started with Carl Powers, the boy who'd been like him, except not, and it had just grown from there, hiding in the back of his mind until it threatened to take over. And while Mycroft didn't approve, he had to admit it was better for Sherlock than drugs or lazing about in a flat all day thinking about them.
So he got himself in with a Detective Inspector Lestrade, a man who'd already known some of his history, being the one who called the ambulance when he overdosed and went into status at the same time, essentially being the one to save him.
But perhaps, in his own little way, he was thanking him.
And Sherlock supposed that Lestrade was not pleased to have a man chasing after criminals, on rooftops and in rather dangerous situations, when he could collapse into a jerking mess at any moment. But there was no stopping him, and he knew that Lestrade figured it was better to at least be somewhat on his trail rather than clueless when Mycroft came knocking, wondering why the hell Sherlock had fallen off a roof.
Sherlock could care less about the danger aspect, because he knew he always had at least 30 seconds, usually closer to five minutes before the full blown seizure began, which was more than enough time to lay down, hopefully somewhere safe.
Except until one day it wasn't.
But really, it was hardly his fault, he was dangling off the edge of a second story roof by his fingertips, unable to pull himself up because of the aching in his arms, and oh perhaps that upwards of 200 pound guy who had been dealing drugs laced with toxins all over the city, killing three so far and landing at least eleven more in hospital. That may have been stopping him too. Because when the world blurred in front of his eyes despite all his blinking, and he could smell coffee, even though there was none, he knew he was screwed. Because while he may have had between 30 seconds and five minutes before the full blown seizure started, he had even less than that before the complex partial seizure began, which could be anything from frequent swallowing to muscle weakness. This occasion, of course, being the latter.
Sherlock could feel himself slipping, and really only hoped that he would be seizing before he hit the ground, because he was really not looking forward to that.
He wasn't really sure what happened though.