It was the little things Sarah noticed.
Having your "friend" show up to tag along on a first date was a big thing. But it was all the less damning for its surrealism. The real clues were all in the details.
(Later, she would sit and listen to late night rants from John and fancy that Sherlock would rather like that bit. Might even be proud of her, cataloging all the details that people would usually miss – well, that men would anyway.)
It was in the way they stood: in each other's spaces so effortlessly, thoughtlessly, despite the tension. It was in the way John's eyes slide past her – catching, yes, but only for the polite amount of time, the expected minimum – before turning back and up, over his shoulder, to catch a darker pair. In the way he instinctively sought out his friend's reactions, trying and failing to make his body language shout annoyance and disregard even as he twisted over himself to watch the man's face.
She thought she'd won that battle for a while, with the way John settled against her when she put her arm through his. He'd smiled, that sweet awkward grin of his, and she'd felt his attention honestly and completely on her for the first time since their date had been invaded. If she were honest, probably for the first time since they'd met.
But that had lasted just long enough for Sherlock to slip away, and then she could feel John tensing next to her. He'd tried to relax, probably convinced himself that he was glad for the departure, but she could tell he was aware of the absence. His eyes were on the crowd as much as on the show after that – the soft, capable gaze of a doctor replaced by a sharp stare that belonged behind a gun sight.
She had to admit, it had been a bit of a thrill to see that dangerous side of a man who was otherwise so … warm toast. She imagined one day swaying that intensity to herself, looking up into those hardened eyes and maybe, just for a second, feeling a palpitation of fear. She'd never really thought of herself as that sort of girl, but then again, she'd never really thought she was the sort of girl to break chairs over people either.
She didn't remember much of the actual fight. One minute, she was watching John struggle with the acrobat, and the next she was gripping John's hand and running. When all was said and done, she was standing in a cluttered London flat, watching clues come together and wondering what the hell had happened to her life.
She was a doctor. In a sleepy little urban clinic that rarely dealt with worse than a sprained ankle or an STD. She hadn't signed on for the adventuring life curing rare diseases in war-stricken countries like some of her medical school friends. She did not lead the kind of life that accommodated police statements and crime scene photos on a first date.
But, in the end, how could she not stay? How often did nights like that happen to girls like her? There was no harm done; why not stay and enjoy the thrill? She could stand to get her hands a bit dirty. Besides, adrenaline and near escapes had a tendency to bond people.
And then there was that foolish hope, which had swelled again when John clutched her hand, at the way he'd looked so beseechingly when he'd asked her to stay. She should have known better, but after all, John had asked her to stay even when she'd given him an excuse. Maybe he actually meant it.
Then again, maybe some of it – how much she didn't really want to admit – was about screwing with a mad genius. She wasn't blind to the way they had instantly forgotten her existence, the way the case was as intoxicating to John as it was to Sherlock. She hadn't failed to notice the way Sherlock's eyes narrowed when John asked her to stay, the flash of oh-so-human possessiveness as he turned away with some smart remark. It was then that all the little clues added up: Sherlock was mad for him.
So maybe she couldn't really compete, but she could revel in the easy attention she could get from John. In the frustration she could inflict on the man who had so captured her dear John's affection and yet couldn't appreciate what he had. Frustration made all the worse because the great detective himself couldn't quite figure out the source. Such a genius, and yet so blind to all the things that really mattered.
It wasn't until after the kidnapping, when the danger had passed and Sherlock was untying her, whispering platitudes that drowned under the hot rush of her own sobs, and John Watson looked up at her with a cavalier grin that should have been fake but wasn't, that it finally hit her. She'd almost died for this man. An amazing, wonderful, strong, caring man, but one who came with a catch like all the rest.
What could she offer against the seductive thrill of the hunt, the heady rush of adrenaline and danger, the fantastic feats of a genius mind always one step ahead of mere mortals? She could see it when their eyes met over her (an instant when, for all John's genuine care for her, she disappeared so completely from their world that she may as well have been part of the chair she was sitting in), could see the truth then as clear as day: she could date John, she could have him, she could even love him, but when the tails of that slick black coat whipped across the rooftops of London, John Watson would always be one step behind.