James Moriarty has never gotten on very well with cracks.

It wasn't the first odd tic that Sebastian realized he had, nor was it the last. At first he just tried to brush it off as James being James and leave it at that. Jim just did stuff like that- obsessive stuff, compulsive stuff, sometimes even obsessive compulsive stuff, all irritating stuff none the less, but he was enough of a broken idiot savant that his brilliance made up for his glaringly faulty manufacturing.

Sometimes, Sebastian wondered if James Moriarty came with a fucking warranty.

He did do some strange things, no two ways about it. Whenever they were in restaurants, he would take the salt and pepper shakers and turn them so they were 'facing away from him'. Sebastian had never asked how he had arbitrarily decided which side was the 'front', and whether or not maybe he had gotten it wrong just one time, so that instead they were both facing towards him, but it was just one of those things Jim did, and it was rediculous to expect an answer that made any sort of logical sense out of his mental chaos, and so Sebastian had bit down on his question and ignored it, even though he did it every single time they were in a bloody restaurant and it did get kind of annoying sometimes.

And then there was his thing about statues. He flat-out didn't like them. Sebastian had gathered up the patience to ask why, and Jim had just muttered something about them being 'shifty' and then walked off, keeping one eye on the stone statue in the middle of the courtyard like it was liable to do something unexpected. This one Sebastian could have almost understood- almost, because a statue was a brilliant disguise, a hiding place in plain sight, and it would be a brilliant idea to take a statue in the middle of the night and then replace it and impersonate it, waiting for the right moment to kill someone and then going back to stillness. So he could understand it to a point. Except then, it ought to have been all statues that bothered James, and it wasn't- there were specific criteria for which statues he found 'shifty'. Metal ones were fine. Clay ones weren't bad at all. Just stone. That didn't make much sense to Sebastian, but by then, he had run out of the patience to ask, so he hadn't.

That and penlights. This one Sebastian just didn't even ask about, mostly because Jim didn't like being thought of as having weaknesses, and that's what it was. A weakness for penlights. He damn well collected them- he thought Sebastian hadn't noticed, of course, but there was a stash of penlights nearly everywhere he went. They wound up under pillows, in cabinets, behind bookcases- anywhere you could fit one. Just everywhere. He bought them, stole them, made them by hand- any time a penlight might become involved, it had to be his. Sebastian hadn't pointed it out. Jim just went about his daily business with three or four penlights tucked into his pockets. This one didn't make any more sense than the others.

But it was cracks that really took the cake. Cracks in things- bookcovers, wooden shelves, priceless vases, the casings of explosives- they drove him so utterly to ruin that it was funny, at first, and then kind of alarming later. Because Sebastian had known he was nuts, before- utterly bonkers- but Jim had always made insanity seem affable and charming and almost endearing in its own way, in-between being slightly annoying. But all of his other compulsive behavior was always kind of cheerfully played down as being just James being James.

Not this.

Sebastian had just noticed little things at first. That he wouldn't step on cracks in the sidewalk. He had thought at first that it was just because of the little children's rhyme about break your mother's back, because James took little children's rhymes and stories and things disturbingly seriously sometimes. There was something terribly odd about a grown man- even a madman like Moriarty- reading a children's book over a cup of tea, and finishing it, and setting it down and beginning to talk about it as though it was the most dryly fascinating piece of historically accurate high literature he had ever read. Like the stories about mad old wizards and plucky young adventurers were actually biographies. But that was still something he did that fell into the affable and charming category of madness, so Sebastian shrugged it off, but none the less he had considered it a possibility when he saw Jim deftly skipping the cracks in the street without looking at them.

But then, he had realized that Jim's mom was missing and presumed dead and even if she hadn't been, he most certainly wouldn't have gone out of his way to spare her any sort of torture on his behalf, not even something as small as changing the way he walked in order to save her from a painful injury, paralysis, and potentially slow death. No, there was something more to it, but Sebastian couldn't for the life of him figure out what it was.

He had started paying attention, after that. Paying attention to Jim, to the cracks, and he realized that the man would walk halfway across a room just to turn a book towards the wall if its cover had a dry crack in the leather binding, and he would do the same with priceless ming vases and even historical relics- twist them around to face the wall, even dispatchig their security measures just to do it, sometimes- and Sebastian had just laughed it off as dear god, another quirk? How am I expected to keep up?

But then the day had come that they had been staying in a hotel. A nice one, with a luxury suite, and a spa, and clean comfortable beds, and a gorgeous view.

There had been a crack in the inner wall of the closet.

James had snapped.

It hadn't been bothering him, it hadn't even been really visible, but Jim had flipped out, and accused the hospital staff of quite a few things that didn't really make a lot of sense at the time, and they had tried to offer their 'displeased customer' a better deal, but those were their last set of rooms so they couldn't upgrade, and they were all really rather sorry about that.

Jim had left. He hadn't stayed, he hadn't taken the better deal, he had just grabbed his stuff and gotten the hell out of there. Sebastian had come with him because that was what he did, through hell or high water, even though they wound up in a little sandy brown hotel off of the main highway and it wasn't anywhere near as nice, but at least there hadn't been any cracks in the walls.

It hadn't been just a weakness or a compulsion. It was a phobia. The biggest NO that Sebastian had ever seen out of James, an absolute refusal for compromise, even when it turned out better for him in the end. He just couldn't do it.

He had asked. Just once. He had asked why.

And Jim had just given him this look.

This look like he had just asked why he was uncomfortable sleeping with an armed nuclear weapon in the bed with him.

Sebastian hadn't asked again. But he had thought. He had wondered, and watched, and thought. And in the end, in a rare, priceless moment of being able to understand James Moriarty, he had come to the conclusion that Jim must have hated cracks because his world was so fractured, so shattered already as it was, that a crack in the surface of reality seemed like the universe taunting him, a string to be pulled on and everything would unravel because there being a crack meant there was something on the other side of that crack, and if he pushed- if he allowed his brilliant, genius mind to push on that mystery just a little too hard, then everything would collapse because what was on the other side might actually come through, and bring the whole world to ashes along with it.

Sebastian couldn't possibly know exactly how right he really was.