Disclaimer: If you recognise it, it was probably created by Sir Arthur Conan Doyle and/or the BBC's talented Steven Moffat and Mark Gatiss.

Author's note: So they've finally shown the series here in Australia. This scene has been rattling around my head for the past week, so I finally gave in and wrote it. I may continue with this if you guys like it, so let me know what you think.

If only he hadn't invited her to join them at the cafe that day. He hadn't intended to do it, had intended to just thank her for her help. She had helped too, listening in on their conversation from the next table and eventually leaning over to suggest a facet they hadn't been considering. He'd been too excited to be offended. He'd known there was something he was missing. Of course, he'd have come to it eventually, but this dropped him neatly into the meat of the problem.

Then she smiled at him, and he felt like someone had just punched him in the chest. So he asked her to move her chair and meal to their table, ignored the startled look on John's face, and started explaining to them both the conclusions her suggestion had lead him to. Seeing John look impressed by his skill was gratifying as always. Seeing the same look on her...

If only he hadn't invited her back to the flat to show her some of the data they'd gathered on the case. She'd followed his reasoning better than most people did on their first meeting with him, though, and he couldn't resist showing off a little more. He'd watched her eyes dart around the room, an odd smile tugging at the corners of her mouth as she spotted the skull on the mantle. He'd asked what she was thinking, and she'd replied, "Alas, poor Yorick?" He'd never even considered giving the skull a name, but he was fairly certain that now it was going to be impossible not to think of it as Yorick.

She'd perched on the edge of the desk, legs swinging and hair shining like polished copper in the firelight, and listened avidly as he'd shown the papers and cuttings he and John had collected and explained their significance. John had kept shooting him amused looks over the top of his screen. He hadn't seen what there was to be amused about, though. It was just so rare to find someone else interested in what he did and how he did it. Come to think of it, John was the only other person who had ever shown this sort of interest. And it was always fun to have a new audience.

If only he hadn't agreed when she asked if she could call again the next day to see how they were getting on. Or the day after that. Or the day after that. He found that he enjoyed her visits though. She'd drop in after work and the three of them would talk over the day's developments for a while. Then the conversation would drift off onto other topics of varying breadth and depth. One night he'd had a breakthrough and had dragged her out with himself and John to have another look at the back yard of a house they'd been to that day. The fact that she was just as eager as they were to climb over the wall impressed him. The fact that she was too short to reach and needed him to haul her up by the wrists amused him.

He'd even found himself texting her during the day when he'd made a particularly brilliant discovery. Only once or twice, but John had caught him at it and teased him about it. John teasing him didn't bother him. Not having an adequate comeback did, so he had decided to ignore it and hope it went away. It was easier than trying to explain how much the excited text he'd get in response pleased him. He wasn't sure he understood it himself.

If only he'd managed to ignore the teasing comments she'd make now and then. The sort of comments he usually could ignore easily, or at least think of a scathing response to. The first had come when he'd asked if she often eavesdropped on people when she was out. She'd blushed and shaken her head, then admitted that the only reason she'd been listening was because of his voice. He'd been confused as to the relevance of this and asked her to clarify, and she'd looked at him as if he'd grown another head and said, "Sherlock, you could be reading the damn phonebook and I'd still be more than happy to listen to you for a couple of hours!" John insisted that he'd blushed in response, but he refused to believe that.

Then there was the time when she'd referred to him in an offhand manner as "tall, dark and handsome". He'd grown more used to her banter by this time and so had given her a winning smile and asked if she really thought he was handsome. She'd fluttered her eyelashes outrageously at him and gushed, "Oh, you're absolutely dreamy, sweetheart!" John insisted he'd blushed at that one too, insufferable man that he was.

If only he hadn't started to return the flirting. It had been a fun side-thread to run while he worked through the case - each of them trying to outdo the other. It was a challenge, and he could never resist a challenge. Surprising how natural it had started to feel, though. He'd always considered that sort of behaviour merely a means to an end. Women often reacted more favourably after a few sweet words and suggestive looks, were more inclined to open their thoughts for him to pick through.

Somehow, though, it was different when the means was the end. When it was just for fun. He'd enjoyed being able to surprise her, enjoyed seeing her eyes widen in shock for that fraction of an instant before she regained control of herself and came back with a laughing response. She had a beautiful laugh, too, not harsh and grating or an annoying giggle.

If only he hadn't let himself lose that emotional detachment he was usually so careful to maintain. If he'd recognised the danger in his constant need to impress her, his pleasure in talking with her and teasing her, the fact that even after almost a week her smile still made him feel like he'd been punched.

If he'd had the foresight (or, to be brutally honest with himself, the strength) to walk away from her sooner, he wouldn't be sitting beside John in a cab and staring at a text which gave an address and finished with: I have your girl.