Once again, I must apologise for how long this is taking to do! The truth is, it's got away from my original story structure and rather than put something out that I wasn't entirely happy about, I had to go over the structure again and again, and write a draft of 3 chapters before finessing the first of them. You have no idea how many drafts of this chapter there were! Anyway, I made it in the end... The next one is pretty much written, so there won't be such a delay.

Couple of explanations - Territorial Army (or TA) is a voluntary reserve force in the UK who can be called upon to serve in the UK or overseas in support of the regular army - it's a popular weekend/holiday activity for certain types of young men who like an adrenaline rush. I don't mean that in a patronising way - I have a great deal of respect for them, as it can't be easy to train while holding down an ordinary job, and they are extremely brave individuals who have been shipped out to Afghanistan.

And Sherlock's observation on John's obvious 'double-takes' refers to a comment made on one of the episode commentaries (I think by Mark or Steven) that Martin is the king of reaction and they have a tendency to look at him and can tell by that reaction whether or not the joke, or whatever it happens to be, will work on the audience.

Thanks to all my lovely reviewers and followers, and the usual disclaimers apply.

Chapter 10: Weakness

As Sherlock strode from the café, he was sure that Sally would be depressingly predictable. And sure enough…

"Oy, you!" She slammed through the door and stalked straight up to him, prodding him unnecessarily hard in the chest. "Don't just walk away leaving me with that information, Fre – Sher – Holmes."

"Oh, for -," Sherlock rolled his eyes as she stuttered. "Why don't you tell it like it is, Sally?" He put his hands on his hips and smirked in a way that was guaranteed to annoy her. "You always thought I was a freak. What has changed your mind? Or who?" he added, as a sudden suspicion formed in his mind, making him glance briefly towards John.

She glared at him. "Alright. I'll say it if that's what you want. Freak."

They both ignored John's sharp intake of breath as they stared into each other's eyes, neither prepared to back down.

Deep down, she'd always despised him, perhaps always would… but there was something else there in her eyes now, lurking beneath the more overt hostility. A grudging respect. When he'd first returned, he'd half expected embarrassment, shame, stammered apologies and awkwardness from her, but he'd forgotten Sally Donovan's sheer bloody-mindedness. She'd never back down or give him the satisfaction of seeing her beaten. And yet… for all that, she was a good copper. She had a strong sense of justice and a determination to seek it out, whatever the personal cost, and that was what made her good at her job.

And it was the same bloody-minded nature that she appreciated in others. She could admire his fortitude against all the odds and his determination to keep his head high amid the accusations, but that didn't mean she had to like him.

Well. He could live with that. It wasn't as if he liked her much either.

Sherlock found his lips curving up, almost against his will. "OK, then. We both know where we stand."

He was amused to see her smile very slightly in response before returning to the more familiar sullen frown. "No we don't. You don't get to make comments like that and then just bugger off. You said another victim, probably today. What the hell am I supposed to do with that? I can't just twiddle my thumbs and wait for it to happen! And what are you going to do?"

John made a slight movement as if about to intervene, and she spun her accusing finger towards him. "You keep out of this. I mean it, John."

He subsided, giving Sherlock a resigned look. Sally turned the full force of her glare back onto the consulting detective.

"You do realise that I'm just about the closest thing you have to a friend on the force right now – and the irony about that is that I hate you. I want to help – no, I do," she added in response to his cynical laugh. "Not because I care about you, but I do care about Greg. He worked better when you were there. He needs you, even if he won't admit it right now. We need you. I acknowledge that. But you can't just mess around the way you used to, Sherlock, treating us like idiots, trampling over everyone's feelings - you really can't. You have to work with us, otherwise you're always going to be an outsider – and there won't be any second chances." Her dark eyes softened, and she lowered her voice. "And you need us too. So, come on – talk to me."

Sherlock sighed. If there was one thing he detested, it was having to stand still and explain exactly what he was going to do, when he could be getting on with doing it. To some degree, John understood that and was able to judge when he should and shouldn't bother Sherlock with questions. The Yarders, however, had never possessed the same insight - they had always viewed his dramatic and unexplained departures as just another sign of his arrogance.

He took a deep breath. "Your second victim is undoubtedly the would-be lover. They are linked, but it might not be due to their brief liaison. I need to find that link – and until I do, it's impossible to predict who the third victim is likely to be."

"But you're sure that there is going to be one," she persisted.

He rolled his eyes. "Well, I'm not entirely sure - obviously. There's always a chance that the murderer got himself knocked down by a car in the meantime. Or perhaps he's at the bottom of the Thames. Who can tell? But yes, if he is still active, there will be a third. He is establishing a pattern – and quite possibly a taste for it."

She gave him a shrewd look. "In that case, I need to tell Greg. You do understand that?"

"Do what you like – but he's not turning me off this case," he snapped, suddenly furious. "Remember, you called me in. You need me to solve this. We're wasting time here."

She blew out a frustrated breath. "You can't even guarantee to find him before he strikes again – not if it's going to be tonight. For all we know, he might be killing someone right now, and we have no way -."

He scrubbed his knuckles across his eyes, suddenly feeling utterly weary. How could he put this without being accused of being an unfeeling monster yet again?

"I can't guarantee to find him in time to save a third person, Sally. But I can – and will – find him as quickly as I can. That's all I can promise you."

He closed his eyes for a moment, heard her sharp intake of breath and waited, wearily resigned to the inevitable insults. Monster. Heartless freak. Psychopath. There are people involved, real people, Sherlock – just so I know, does that mean anything to you? You...machine…

"What can I do?"

He opened his eyes to see her observing him gravely. It may have been the first time ever that she had looked at him without an expression of disgust or open anger or derision on her face.

He sighed again. "You really want to help? Then, let me do my job. Try to keep Greg off my back if you can. Get your patrols mobilised. And – this is just a suspicion at present - but get some officers down to Kingston University to round up the other students on that summer programme."

"You think the third victim may be among them?"

"It's a distinct possibility."

She looked at him for a long moment and then nodded briskly, seeming to make her mind up. "OK. I'll get onto that. I'll be at the Yard, getting Greg up to speed. You-," she prodded Sherlock again, hard enough to make him wince, "– keep me updated and as soon as you have any new information on the killer or any potential victims -."

"Yes, yes," he interrupted, impatiently. "Come on, John."

As he turned away to hurry to the nearest main road, in search of a taxi, he was aware of a wary look passing between Sally and John, but she said nothing else and after a minute, John hurried after him.

"So you think there'll be someone else today? Do you have any clue who, apart from a half-formed idea that it might be another student?"

Sherlock threw him an impatient look. "No – of course not. If I did, I'd tell her. I only observe that there is a pattern. Both were killed on a Saturday two weeks apart, with the second victim two weeks ago. It could be significant."

"It might not be, the days might be a coincidence."

"Yes. That is also a possibility." He almost said I need more victims to be sure, but managed to bite his lip in time.

"But -."

"But what?" Sherlock stopped and swung around so quickly that John almost bumped into him. "What do you want me to say, John? Are you going to accuse me of not caring about the third victim, because if you are, you need to stop now. You know by now how I work. I can't fundamentally change that, and I need to investigate this in my own way. I won't change, John." Not for you. Not for anyone.

"I wasn't going to say anything! Only just… if you have any idea – any idea at all…" John was trying but failing to hide the anxiety in his eyes.

"I don't. Not yet."

John took a deep shuddering breath and glanced at his watch. "So, where now?"

"Kingston University." Sherlock raised his arm and felt a certain degree of satisfaction when a black cab pulled up immediately. He heard a quiet snort and gave John a side-glance; the doctor's lips were twitching suspiciously, almost as if he had read the detective's body language.

It was true that Sherlock felt an energy fizzing through him that he hadn't felt for a very long time. It was the siren call of the Work; that incessant buzzing sensation under his skin that told him there would be no rest for him until the case was solved. It was not a sensation that he could easily put aside. He was not being stubborn in refusing food or sleep while on the Work; it was, quite simply, that his mind would not allow his body to partake. The Work took priority; it had to take priority – and not just because it was likely that someone else would lose their life today, if they hadn't already.

It wasn't news to him that John was able to recognise the signs so easily, but as he entered the taxi, his feet stumbled a little as he had a sudden revelation: yes, John understood, but did he feel the same compulsion? Or had he merely always followed behind, putting up with the hours of tedious investigation and the missed meals and interrupted sleep for the sake of the addictive adrenaline that would accompany the inevitable chase? Before the fall, Sherlock had grown used to John following him, to the degree that it felt utterly natural… but John had his own life these days. Would he still be prepared to follow without question? And what did that adrenaline rush mean to him now anyway?

John followed him into the taxi and settled back, seemingly unaware of his momentary hesitation. "You really think that summer school is the link, and not their relationship – such as it was?"

"Obvious." Sherlock gazed out of the window as they proceeded slowly down Shepherds Bush Road, not really seeing the stop-start traffic. "The sexual encounter is a red herring. If it had been significant, one of them would have been targeted, not both. If an illicit sexual act is the reason for murder, it is not usual for both participants to be murdered at different times. More likely they would be killed together with a considerable degree of violence – a genuine crime of passion, if you like. No, they were killed at different times and in different locations, so it's for another reason."

He leaned back, warming to his theme. "She was alone when she left the concert. This wasn't a random murder – she was known to her victim. He knew exactly where to find her and when. No sexual assault or gratuitous violence. More of an assassination," he added, thoughtfully. "Someone decided the world would be a better place without her. He took no pleasure in her murder. It was an unpleasant task to be done – and he did it efficiently. Surprisingly so for an amateur."

"An amateur? You think so?" In the window's reflection, Sherlock saw John shift and give him a surprised glance.

"You don't?" he murmured at the glass, not bothering to look around.

"Well, I thought, when you said 'assassination' that perhaps the husband - ."

"Not involved."

"You can't know that! How can you be so sure without even seeing a transcript of his interview?"

"Because he would have hired a professional. This man was not a professional, as evidenced by the sloppy attempt to dispose of Kimmel's body. He'd probably learnt a good technique for the murder – I suspect he may have been in some form of military service at some point where he learnt hand-to-hand combat, Territorial Army most likely – but his training didn't cover how to get rid of inconveniently dead bodies. He didn't know what to do with it; initially he stored it in a location where there was a significant risk that the stench of decomposition would attract attention. Probably a workshop or a garden shed. Hence the insecticide – to disguise the smell. It must have been a shock to him when the body did not decompose – or rather I should say bodies, as undoubtedly her would-be lover had joined her by then."

"So you're certain that this other student is the unidentified man?"

"Yes. Mark Hodder." Sherlock drummed his fingers on the window frame, impatient to be there. "Post-graduate student, architect by profession but not a particularly successful one, from Chicago. More interested in luxury speedboats and other possible business deals than in either art or architecture."

He smirked at the glass as he sensed John pondering his words. John was the unacknowledged master of the 'double-take'. If Sherlock had ever wanted to know how the 'ordinary' person would react to a comment or a revealed fact, John's reaction would always tell him everything he needed to know. There was a time when the doctor would have reacted to Sherlock's deductions with obvious surprise – would have been openly incredulous or admiring, muttering the ever familiar 'amazing'. He was less effusive these days, and a little more reflective - one of the many tiny but significant ways in which he had changed during Sherlock's years away.

"You looked him up in Sally's notebook," John said, finally. "When you asked her for a time of death for the second murder – didn't you? I wondered why you leaned towards her like that. You must have read it upside down while she checked."

"Of course I did. Obvious," Sherlock snorted, but he smiled very slightly all the same.

They were both silent for a while, lost in their own thoughts. As the taxi weaved its ponderous way through the heavy traffic, the atmosphere was strangely peaceful despite the urgency of their objective. Sherlock wondered at his own sense of ease, lying just beneath the more familiar thrum of excitement caused by the thrill of an unsolved mystery.

He had rarely been entirely at ease in his life. Even before the fall, there had always been too many topics occupying his ever-buzzing mind – cold cases, new experiments, endless deductions to be made, even his music didn't always give him much tranquillity. There might be moments of satisfaction caused by a good deduction or an expected result, but they did not lead to ease – not mental, anyway. His mind, if not his body, was in perpetual motion - it always had been, from his earliest memory. John's eighteen-month presence at 221B before the fall hadn't changed that. It had only been in the later months before the fall that he had allowed those peaceful, meaningless Sunday evenings, with the takeaway and the terrible TV programmes, to take over his life - mind, body and soul - for just a few brief hours.

He frowned a little. During the last few months, he'd forgotten just how much he'd missed those Sunday evenings before the fall, and he wasn't sure that he cared for the reminder. John had tried to return to their old life, and no more so than with the Sunday evening routine, but Sherlock had been awkward, refusing to join him to eat, and downright sulking on occasions. He had actively resisted falling back into that comforting old routine – but why?

He turned and stared at John. The doctor was gazing out of his own window, seemingly unaware of his friend's gaze. Or perhaps it might be more true to say that he was aware but tolerated it. Was John so used to being deduced that he no longer paid it any heed?

To the untutored eye, he looked completely relaxed, but Sherlock knew better. His posture was one of 'watchful waiting', as Sherlock always termed it in his mind. The off-duty soldier, seemingly at rest and happy to sit back and observe, but ever alert to the slightest danger, simply as a force of habit left over from his Afghanistan days. His gaze, apparently unfocused, was deceptively sharp, his eyes running over the passing pedestrians. Looking for…what? Bulges in clothing that might be concealed firearms? A familiar face in the crowd? His shoulders were tense, his body ready to respond in a second.

It was a familiar pose… and yet, there was something different. Something missing… and Sherlock found his mind returning to his earlier, uncomfortable, revelation.

What did John get out of this?

"Could be dangerous" – that's what he'd said all those years ago, by which he'd really meant "could be fun". Back then, that's all it was – the thrill of the chase, of 'solving the unsolvable', of making fools of the Yarders… He was young, at the height of his powers, he was invincible. 'Dangerous' had been a remote concept – he might have got himself into hazardous situations, but he would always be able to use his considerable wits and physical prowess to get out of them too. That was before Moriarty.

Could be dangerous. And John had come running, because he had felt the same siren call. And he had loved it – the midnight chases, the standoffs, the fights, the laughter over a takeaway once the case had been solved. Sherlock had recognised a kindred spirit in him from the moment they had met – that same restless need for adventure. He'd had seen it in the limping doctor's eyes after that first chase - sparkling, suddenly alive. John had an extraordinarily expressive face and even at the most dangerous moments, whenever he had slipped into his 'watchful waiting' pose, his eyes had always glittered with that same excitement.

John's head turned suddenly and his eyes met Sherlock's in mute inquiry. And Sherlock realised, with a sinking feeling in his stomach, exactly what was missing. The eyes, still keen, were harder now. There was no spark.

At some point, during the last three years, 'danger' had stopped equating 'fun' for John.

The doctor frowned at the scrutiny and his mouth opened, forming a question that was just as quickly swallowed. The initial confusion in his face cleared to be replaced by a rather odd, blank expression. Sherlock dropped his eyes quickly; as he looked away, he wondered what it was that John had seen in his own expression that had stopped him asking his question.

"He was right, you know."

Sherlock glared without bothering to look away from the glittering water. "Piss off, Mycroft. Don't you have rogue nations to terrorise?"

He was leaning on the Serpentine Bridge in Hyde Park, taking a break from one of his furious walks across the city. It had been two months since he had been accosted by his brother outside Bart's on the same day that Lestrade had ousted him from New Scotland Yard. Since then, he'd heard nothing from Mycroft. Too bad the idyll was clearly over.

He heard his brother's heavy, rather ponderous steps on the wet tarmac as he approached. "Moriarty. He was right."

Sherlock sneered. "You surprise me. About what?"

"Your weakness." Mycroft leaned on the bridge next to him and peered down at the ducks with some satisfaction, as if their continued peaceful existence was entirely down to his own diligent efforts. As well they might be.

"I don't want to hear it, Mycroft, whatever your latest ridiculous theory might be."

"Caring is not an advantage," Mycroft said softly, putting a faintly ironic emphasis on each word, as if he was quoting someone else's words. "Do you remember the very first time I said that to you?"

He remembered. Oh, how he remembered.

"I was nine."

Mycroft was silent for a moment before continuing. "You…asked me why Mother did not appear to love you. You were old enough by then to recognise that her behaviour was not that of a normal parent, but not yet old enough to understand why… or to care. You were more fascinated than hurt by it."

"She did not want me. She never wanted me." Sherlock stated the matter flatly. It had ceased to hurt a very long time ago – if it had ever hurt. Had it simply been the excuse he had needed for the drugs? The psychiatrist had certainly thought so, in that dreary place that Mycroft had forced him to enter for rehabilitation. The over-intelligent younger son ,whose mother had once contemplated abortion and had always regretted not seeing it through. The behavioural problems, the social deficiencies. Textbook case.

"That aside," Mycroft's dry, emotionless voice broke across his thoughts almost brutally. "The reality was that you sought an answer that I was - perhaps - ill-prepared to give at that time. I was about to go away again - to University. I wouldn't be there any more to act as a buffer between the two of you. So, I did what I thought best in the circumstances... You required an answer and I told you that it would not be advantageous for you to care about her lack of love for you. If you had cared, you would have grown bitter. It would have dominated your adolescence … and you were so bright, Sherlock. So full of life and energy. I couldn't -."

He broke off and peered intently at the water, focusing very carefully on a great crested grebe as it passed underneath the bridge.

"It occurs to me," he continued, very quietly, "that you may have taken that advice to heart."

Sherlock gave a brief, mirthless laugh. "You repeated it to me enough times over the years. So, tell me -," his voice took on a mocking quality, " – what was my weakness? Oh, let me guess. He exploited the fact that I cared far too much for three people. Enough to throw myself off a building for them. It's old information, Mycroft. I know. So yes – you were right and I was wrong. Congratulations, dear brother. Caring really isn't an advantage."

Mycroft continued to lean silently on the rail, not looking at him. After a minute of this, Sherlock gave an impatient huff and turned away.

"Has it ever occurred to you," Mycroft called after him. "- that I may have been wrong?"

John cared about him. He hadn't at first – oh, he had in the sense that he wasn't prepared to allow a slightly mad consulting detective die needlessly at the hands of a psychotic taxi driver, but that was just John. The soldier; the doctor. The decent man. It had had nothing to do with Sherlock.

But later on, yes, he'd cared. And Sherlock hadn't seen it, hadn't wanted to acknowledge it as the months passed. There had been that moment, just before Moriarty had struck again so fatally. "It really bothers you what people say about me? I don't understand – why would it upset you?" And John had said nothing for a moment – had just given him that same, slightly blank look. That look that meant yes, it was fun once…when it didn't matter so much.

And now that it did matter and it wasn't fun anymore… what did that mean? Roof-top promises were one thing, but in the clear light of day, when there was a job to be done, where would John be? Would he still be there, hurrying obediently after Sherlock, or would the day come when he would decide that it just wasn't enough anymore – not for him? Or that he simply couldn't bear to continue watching Sherlock plunging into danger?

And was he still Sherlock's great weakness - the one person for whom he would give up any case, relinquish any fight? Was there another Moriarty out there somewhere, preparing to exploit that once more?

As they crossed Putney Bridge, the subject of his musings cleared his throat and appeared determined to change the tense atmosphere. "How did you know that Hodder was killed on the 13th?"

"Easy. Exactly two weeks after the first murder."

John frowned. "You mentioned that before. You think he – I assume it's a he? – picked those dates deliberately?"

"Not so much the dates as the days. Both Saturdays."

"What – so the guy only kills on his day off?" John laughed, a little uncertainly, as if he was unsure whether Sherlock would take the lame joke well.

Sherlock restricted himself to a mild huff of irritation. "This man compartmentalises his life. He works, almost certainly full time, Monday to Friday, sometimes evenings during the week. He also works late every other Saturday. These killings have nothing to do with his work life – in fact, he takes a great deal of pride in his profession and wouldn't want to see it tarnished by something so…distasteful. So alternate Saturday nights are his time. And look at the murders. Elisabeth Kimmel was killed in an extremely clean and efficient manner. No unnecessary injuries, minimal blood loss. Mark Hodder will have been dispatched of in a similar manner, no doubt. This man takes no pleasure in his kills. There's no sadism there. And the manner of their disposal. She was cleaned to the best of his ability and disposed in an orderly manner. Again, I'd have to see Hodder's body, but – actually, that's a good point -."

He broke off to send a quick text to Molly.

"And why not Sunday?"

Sherlock shrugged. "Another day, another man – quite literally, in his view. I suspect he goes to church."

John whistled his disbelief. "Not very Christian behaviour."

"Hmm." Sherlock stared blankly out of the window. After a minute, he said, as a sudden revelation came to him: "He wants to be found. He – what he has become… He wants it to stop. Why does he want it to stop? It's not natural to him. It disgusts him – the act of killing – and yet, now that he's started, he can't stop. And why remove her clothing? There was no sexual element. No, it was because he wanted to clean her, to try to wipe away his act of violence. No doubt he did the same with Hodder's body. And the clues -"

"Are they aimed at the police?"

"Yes." Sherlock frowned. "Or perhaps not precisely at the police. This individual wants to justify his acts to the world at large. And he hides behind cultural references to do so. This is not a worldly man. It's a…confession, if you like."

"Oh? A Catholic, then?"

"Possibly." Sherlock shrugged; religious motivations had always discomforted him a little because he couldn't understand them even remotely. It was possible that John had a greater understanding, as a doctor who had treated people with a wide variety of cultural and religious beliefs. He dismissed this line of inquiry, moving quickly onto the facts. "The first murder is easy to interpret. That quote from Johnson's London. As you suspect, the lines relate to the victim. He probably believes that the victim did, quite literally 'taint the heart'."

"And where she was left? The bookshop?"

"Possibly significant. The murderer clearly knows the location and its proprietor. He may know that the shopkeeper is German, even though he has lived in Britain for most of his life, sounds English and has adopted an English name - he may even know that he has sought to hide a family background that he considers shameful. However, I don't think our man intended the shopkeeper to come under suspicion – it was merely the location and quite possibly the nationality of its owner that was symbolic."

John considered this for a moment. "And the second murder?"

"The message is a little harder to interpret. A painting – well, he was clearly on an art-related course. He had probably visited the National Gallery as part of his study. As for the painting - The Thames Below Westminster…" He frowned.

"He was found by the river," John put in, helpfully. "And was interested in speedboats."

"Irrelevant. The gallery he was left in was the key… but I can't see any link between that and the bookshop… "

John paused, frowning. "Actually, there is -."

But he was interrupted by the taxi driver, who pulled in suddenly. "Here you go, gents."

Sherlock looked up at the University building, putting his hand on the door latch to open it. He glanced back at John. "What were you going to say?"

John stared blankly at the seat in front of him for a moment, before shaking his head. "Nothing. I thought I had something, but it's gone." He shrugged. "It probably wasn't important anyway."