"Affairs?"

Lestrade took the mug John handed to him with a muttered, "Thanks," but didn't take his eyes off Sherlock, who was stretched out indolently in his armchair, still unimpressed that Lestrade hadn't turned out the night before to witness his genius.

"That's what I said," he drawled in response. "Am I being unclear?"

Lestrade threw a glance at John, who took pity on him. "Richard Simpson, Philippa Saunders and Moira Pickering were all having affairs which were officially kept secret because their partners were married," he explained.

"A lover who doesn't stay over," Lestrade remembered, turning to Sherlock. "That's what you said in Miss Pickering's flat, because her bed was in the corner."

"Yes," agreed Sherlock. "Oddly enough, I do actually recall statements I made only three days ago."

John moved over to the fireplace, kicking Sherlock's foot en route and getting a reproachful look in return. He indicated their copies of the 'I'm Sorry' messages, which were now also taped to the wall. "All three of them wrote an apology before they were killed," he said.

Lestrade walked over to join him, his eyes running over the rest of the notes. "Good grief, Sherlock, your handwriting's actually getting worse," he commented, taking a sip of his drink. "And I honestly didn't think that was possible."

Sherlock sniggered, his mood significantly improved by John's indignant expression. He got to his feet. "Not only do you now fail to recognise the typically illegible scrawl of a doctor," he told Lestrade, who gave John an apologetic grimace, "but none of your team managed to spot that this note," he indicated the one found at the scene of Neil's murder, "was not written by the victim. You only checked the first one, didn't you?"

Lestrade stared at him. "So, who wrote it?"

Sherlock just gave his enigmatic smile.

"Hang on a minute," Lestrade said slowly. "I spoke to Helena Bagshaw, and to Neil Benson's colleagues - it didn't sound to me as if he was having an affair with anybody."

"Indeed," confirmed Sherlock. "But he was regularly spending the night in a hotel room with a married woman, wasn't he?"

Lestrade's expression echoed the 'light bulb' moment which John had already been through. "So the murderer..."

"Made a mistake," Sherlock finished. "Which raises some interesting questions, don't you think?"

John and Lestrade both nodded, each hoping they weren't going to be asked to come up with any.

Switching back to his original query, Lestrade pointed at the odd 'I'm Sorry' message again. "So, who did write it?"

"Surely it's obvious?"

"Oh, get on with it!" sighed John.

Sherlock huffed. "What is the message?" he demanded, immediately answering his own question: "It's an apology. In three of the cases the victims were made to apologise for being involved in an adulterous relationship. But when it came to Neil Benson, there was no affair - the man was still in mourning for his late wife, which the murderer would quite likely even approve of."

He was pacing back and forth now, both John and Lestrade following his movements. "But by the time he's proved his innocence - got out his AA chips, shown off his photograph albums - it's too late." He stopped and looked at them. "He has seen the killer and must therefore die. So - who needs to apologise?" he asked. "Who has made a mistake and might even feel remorse about it?"

Their eyes turned to the wall, as if the note itself might suddenly develop murderous intent.

"So, we've got the killer's handwriting," Lestrade surmised, thinking about it. "But that's not actually going to help us find him, is it?"

Sherlock sat back down in his chair. "Sadly, no – although it should help with a conviction," he pointed out. "But knowing his victim profile is the useful thing at this stage – the handwriting discrepancy proves that Neil Benson was indeed the odd one out, so we've definitely got the right motive. The killer is targeting people who are involved in a sexual relationship with a married partner, although they themselves are purportedly single."

John's stomach rumbled loudly at this point and he rubbed it ruefully, ignoring Sherlock's frown at the human weakness intruding on his commentary. "Have you had breakfast yet?" he asked Lestrade, who nodded.

"I'm fine with this, thanks." He raised his mug.

"Well, I'm starved," John said firmly, aiming his words in Sherlock's direction. He bustled off into the kitchen and soon the rattle of the fridge door was interspersed with cupboards banging and a variety of curses. "Damn, it will have to be toast. Can I have some honey?" he shouted through to Sherlock over the noise of the kettle.

Lestrade was extremely taken aback by the endearment, but he tried not to show it. "Is the toast rationed?" he enquired, sitting down in the other chair and adopting a blasé tone.

"You're inserting a comma where no comma exists," Sherlock told him disdainfully, after calling through an "Of course," to John. "He's asking about the honey, not the toast." He waited while Lestrade worked that out. "The honey is supposedly mine – I don't buy it, but he's trying to instil a concept of ownership and respect for other people's property." A mischievous grin appeared which Lestrade found quite disconcerting on Sherlock's face. "He's not having much luck with it."

John returned soon after, plate in hand. "Out of jam," he explained, taking a bite of his toast then moving over to the fireplace. He set the plate down on the arm of Sherlock's chair and picked up a pen, adding a couple of points to the details about Neil's flat before going back into the kitchen.

"So, there are two different types of link," said Sherlock, absently picking up a slice of toast. "The first of which – what he's looking for in a victim – we have now established." He bit into the toast as John returned and pressed a mug into his other hand.

"Right," agreed Lestrade, watching as the toast disappeared with impressive speed.

"The other link is how he finds them," Sherlock continued, taking a mouthful of his drink, then pulling a face. "John, this is tea," he complained.

"Truly, you're a wonder," agreed John.

Sherlock scowled at him. "I specifically wanted coffee."

"Well, you specifically didn't say so."

"I didn't say I wanted tea, either."

"Give it here." John swapped their mugs. "You all right?" he asked Lestrade, nodding towards his drink.

"Oh, fine," Lestrade said quickly, finishing it off before John could decide to give it to Sherlock instead. He felt rather as if he'd wandered into a well rehearsed play and was the only one who didn't know his lines.

"There must be thousands of people in London who fit the killer's criteria," Sherlock continued, getting to his feet again, "but how does he find out who they are?" He sipped his coffee, then set it down on the mantelpiece. "The three actual affairs were kept quiet and the other was non-existent, so how is he learning about them?"

Lestrade considered. "Well, we've already established that they had no common links, so it's unlikely that the killer knew them personally - especially Neil Benson, of course, or he would have known that he didn't fit the pattern."

John was looking at the notes again. "They all worked at different places, but their offices aren't actually that far apart," he pointed out. "I mean, they're not on the same street or anything, but they all worked in the city centre."

"Offices..." Sherlock muttered. "Offices... Yes!" He grabbed John's shoulders. "Brilliant!" he declared, beaming down at him. John concentrated on not spilling his tea and Lestrade got to his feet - it felt wrong to be sitting when there would clearly be whirling going on.

"No smoke without fire, they say, but they were wrong about one of them," Sherlock said, releasing John and striding a few paces away.

"Who's they?" asked Lestrade.

Sherlock turned and stared at him. "Gossips!" he replied, in his 'did you leave your brain in bed this morning?' voice. "Office gossip is what this killer has access to." He marched back to the wall and pointed at the photo of Richard Simpson. "Number One was an office manager and was involved with someone who worked next door." His finger moved on, stabbing twice more. "Numbers Two and Four both worked in large companies and were having affairs with their employers." Finally he indicated Neil's image. "What did Helena Bagshaw tell us about Number Three?" he prompted John. "About his job, I mean?"

John thought back, remembering the tragic story. "She said that he didn't need it, that it was just to keep him occupied," he replied. Sherlock made a 'keep going' gesture with his hand. "And that her husband helped him to get it... Oh - because he worked in the same building!"

"Exactly!" Sherlock confirmed. He spun on his heel and stepped over to the desk, leaning over John's laptop and tapping away. "Right," he said, scrolling down a page of company information, "Helena's husband is actually the CEO." He swivelled the laptop to display an image of a solid looking man in his fifties. "You can imagine the gossip flying around when his wife was spotted with the office junior."

"Fantastic!" said John, who now had the plate of toast in his hand again. He moved closer to peer at the screen, setting the plate down on the table. Sherlock preened slightly, having been assured by John that false modesty just looked weird on him. He straightened up, taking the last slice of toast, and headed back to their impromptu notice board where he stood and contemplated the locations of the offices in question.

Lestrade forced himself to focus on the case and not be distracted by the stealth-feeding ritual going on in front of him. "So how do we find him?" he asked.

"Legwork," Sherlock replied, picturing Mycroft's expression at the concept. A glance at John showed him sharing the same thought and they both smiled.

"Get a bloody room," muttered Lestrade.

"We live here," pointed out Sherlock, as John picked up the now empty plate and took it back into the kitchen, casting a reproachful glance at Lestrade en route.

"You've been looking for links between the victims, but what we need to find are links between the companies they worked for," Sherlock instructed. "Did they all use the same security firm? Is the same man fixing all their photocopiers? There must be something." He picked up his coffee.

"Right," agreed Lestrade. "Well, I'll go and get cracking on that, then." He patted his coat pockets, checking he'd still got everything he came with, then went and stuck his head into the kitchen. "Thanks for the drink, John," he said. "Stick with him, won't you?"

"Absolutely," said John, moving back into the living room. " Do you want me to have a look at your knee before you go?"

Lestrade was startled, not having realised that he'd been favouring that leg. John was getting as bad as Sherlock, although perhaps just for medical issues.

"It's all right, he just banged it on the bookcase in the hall," Sherlock reported. "Trace of paint on your shirtsleeve where you caught your balance," he explained, at Lestrade's confused expression.

"Damn!" Lestrade looked at his cuff angrily, ""Why does your bookcase have tins of paint instead of books on the shelves?"

"Mrs Hudson's nephew is redecorating," John replied. He indicated the bruise on his forehead. "You're not the first casualty."

"I don't know why she got him that bookcase anyway," Sherlock grumbled, suddenly feeling unaccountably irritable. "Peter never reads anything but Auto Trader."

oOo

The next twenty-four hours were spent asking questions, but getting no useful answers. By the time Sherlock and John walked into Scotland Yard on Friday morning, the only thing getting closer was the weekend.

Hopkins' voice was audible as they approached the incident room. "But the other detectives get to wear plain clothes, Sir."

Lestrade responded just as they stepped through the door. "I'm sorry, Hopkins, but I've told you before - you just look too young. No one believes you're a police officer when you aren't in uniform."

"Even then, they often assume you're just a particularly low-rent kissogram," Anderson added nastily.

Hopkins ignored him, his shoulders sagging slightly at Lestrade's refusal, until he noticed the sudden silence and turned around, a wide smile spreading over his face as he saw Sherlock. The reaction was not a common one. The whole team was there and John noticed Sally moving as far away as the room would allow, while a low murmur built up among the other officers.

Lestrade raised his voice. "Right, Press Conference," he announced, waiting for silence. "Which is in half an hour. Those of you not involved, please carry on with what you were doing yesterday - Sunday is fast approaching and we need to find this guy." The room emptied out considerably.

"Will you come and watch at the Conference?" Lestrade asked, turning to Sherlock. "According to the profilers, it's the sort of thing a serial killer might attend. Will you watch? See if you can spot anyone?"

Sherlock curled his lip at the mention of criminal profiling, which he felt was a complete waste of time, but nodded his agreement. "What information are you planning to release?" he asked.

Lestrade shrugged, looking frustrated. "What information have we got? 'If you're having an affair, don't let anyone in on Sunday'? It's not much."

"Is that wise?" Sherlock asked, his tone clearly saying 'That's stupid'. "If you give out that victim profile, you're going to get copycats."

"It's a risk, but what else can we do?" demanded Lestrade. "We have to warn these people."

"Do we?"

Hopkins had sidled round to John, not wanting to draw attention to the fact that he was still in the room. "Do you understand this?" he muttered under his breath while Sherlock and Lestrade carried on arguing.

"Think about it," John advised quietly. "People who meet this criteria may already have some very specific hatred directed towards them." He glanced sideways at Hopkins, who was clearly listening but kept his eyes on Sherlock. "Imagine if you were married and knew your partner was being unfaithful," he suggested. "Or even the older generation," he added, after a moment's thought. "If your son or daughter was having an affair, and you feared losing your grandchildren if the marriage broke down. Those sorts of strong emotions can lead people to desperate acts - if they're told on the news that a serial killer is targeting the very people they despise, not all of them may stop at just hoping for a particular victim."

"Some might think this is the one time they can get away with it." Hopkins started to nod. "A golden opportunity - like in The ABC Murders, but taking advantage of the situation rather than creating it."

"Exactly," said John. "That's what Sherlock's worried about."

Hopkins exhaled. "He's brilliant, isn't he?"

"I've always thought so."

"One thing our favourite psychopath - sorry, sociopath - has not explained," Anderson's snide voice spoke up loudly, "is how the killer knew the victims would be alone on the Sundays."

Sherlock spared him a glance. "Are you attempting to use both brain cells at the same time again, Anderson?" he enquired. "You know that never ends well."

"Well at least I know the Earth goes round the sun!" snapped Anderson with a customary lack of originality. John winced. Every time the bloody man trotted out that line it reminded Sherlock of what he still felt was a personal betrayal. John wished he'd never put it in the damned blog.

"So says the man who, when asked for a country beginning with Q, suggested Cuba," chipped in Hopkins, managing to silence the room.

"Nice," whispered John, as Lestrade's lips twitched. Even Sherlock looked a little impressed, before he dismissed them all with a wave of his hand.

"The victims were all involved with people who were married, some of them with children too," he said, answering the original question. "If you're somebody's guilty secret, then you don't get weekends." A few eyebrows rose at the edge of bitterness in his tone and Sherlock deflected the attention immediately. "Do you, Sally?" He turned to look directly at her for the first time since entering the room and she practically hissed in outrage.

Lestrade intervened at once. "For God's sake, you two, will you sort it out?" He focused on Sally. "I've cut you a lot of slack in view of what happened, but you're going to have to get past this," he said. "Now, go and check everything's set up in the conference room."

Sally picked up her papers and stalked out, still seething, with Anderson on her heels.

Lestrade sighed heavily. "Right," he said, turning back to Sherlock. "Any more thoughts on the timing? The profilers say that Sundays must have some sort of psychological significance to the killer."

"That could be true," Sherlock conceded. "But it might simply be his day off." He shook his head. "The fourth victim was killed between six and midnight, but definitely drugged before noon, while the third died in the morning. Sunday evening may be his normal kill time, but he's getting to them earlier."

"So what's he doing?" asked John, who'd been unable to get this thought off his mind since the disturbing revelations about the drugged tea. "Does he have to work up to it, or is it some kind of ritual - one that takes him all day?"

"There's no evidence of sexual assault, or of physical torture beyond the bound wrists," Lestrade reminded.

"No, but he must be doing something," said Sherlock. "That would explain why the third victim was killed in the morning: once his 'innocence' was established, the ritual was curtailed."

Lestrade rubbed a hand across his forehead. "So we can warn people who live alone, between the ages of, what? Eighteen and Forty? Fifty?" He looked around and got nods. "And who work in an office – to be vigilant on Sunday, don't admit any strangers to their home, and if possible spend the day with friends or family."

"If that will settle the press," agreed Sherlock, "but it will make no difference." The others looked at him and he shrugged. "There are the paranoid few who would be on guard anyway but the majority will just carry on, confident that murder only happens to other people." He raised his hands in a 'what can you do?' gesture. "Human nature. Just as well, or we'd never catch him."

oOo

He didn't spot anything suspicious at the Press Conference, other than a cameraman who turned out to have five grams of coke inside a roll of film. Lestrade and John were both equally relieved that Sherlock was not alone when this discovery was made and both breathed easier once the drugs had been safely confiscated and taken far, far away.

Sherlock rolled his eyes at them. "Checked the skull yet, John?" he asked sarcastically, then groaned when he saw Lestrade's head flick round. "Wonderful, now you'll both be at it."

It was late morning by the time they got away and John caught Sherlock's arm as he was about to hail one of the taxis which seemed to be vying for his attention. "Can we walk for a bit?" he asked. "I know it's cold, but it's a beautiful day and I could use some fresh air."

Sherlock pulled a face but complied, tightening his scarf and pulling his collar up. "You'll have to give me my gloves back, then," he requested. "The ones I lent you on Tuesday - my others are at home."

It took John a moment to follow that one, then he looked outraged. "You didn't lend them to me, you cheeky sod! You used them to wedge that teacup into my pocket so you didn't have to carry it yourself!"

"Do you have the gloves or not?"

Still grumbling, John produced them, watching slightly enviously as Sherlock pulled them on.

"Where are yours?"

"I'm fine," John stuffed his hands into his pockets.

Sherlock sighed. "What is the point of my repeatedly buying you gloves if you're just going to give them away?" he demanded. "Do I have to have your name sewn into them? Or put a string through your coat with one tied onto each end?"

"Did you have mittens like that as a child?" John asked, suddenly picturing a little boy with unruly curls and bright eyes, all bundled up for the snow.

Sherlock threw him an amused glance. "Whatever you're visualising, I'm sure I never looked anything like it," he said, unexpectedly assailed by an image of a small John - well, small-er, he couldn't help correcting - complete with red nose and gleeful smile, stockpiling snowballs before leading his tiny troops to victory. He blinked to clear the ridiculous vision from his mind, and lengthened his stride.

John mentally tried to add a smirk to the little Sherlock in his head, who was now using the string from his mittens to set up some kind of ambush, but it came out more mischievous than superior. The ambush must be for Mycroft, but John's imagination baulked at picturing him as a child - the best he could manage was a slightly shorter version but still in a three-piece suit, his bowler hat slipping a little too low over his eyes.

They were walking through Green Park by this time and John's mind was wandering. "Do you think we would have been friends if we'd met when we were younger?" he asked.

Sherlock frowned as he thought about it. "I would estimate..."

"That still means guess, you know," John chipped in.

Sherlock didn't miss a beat. "I would judge, based on a range of factors which would take too long to explain to you, that it would be... unlikely," he said and there was an odd note in his voice.

John looked at him curiously. "Give me some of the factors," he requested.

It was a while before Sherlock responded. "When I was in my twenties," he started, the words emerging with obvious reluctance, "there would have been little for you to admire." He fell silent, and it was clear that he did not intend to elaborate. "Also," he stole a quick glance at John, "I'm not sure that I would have recognised you."

"Recognised me?" John was confused, but Sherlock didn't say any more. "What about younger?" he asked, eventually. "School age?"

"What's brought this on?" Sherlock enquired. "You're not usually given to such philosophical musings."

John shrugged. "I don't know," he said. "I guess I've been thinking a bit about fate, and so forth - you know, what if we hadn't met when we did? Or what if I hadn't gone into the army? I wouldn't have learned how to shoot; I wouldn't be as useful to you..."

"And I would be dead," Sherlock finished. "You've been watching too much Doctor Who - this is that episode about turning the other way at the junction, isn't it?" He shook his head. "Why Harry would buy you such a juvenile gift I cannot comprehend."

"She knew I used to watch the old series and thought I might like to catch up with the new ones," John defended. "And I do like them. Doctor Who is classic telly, it's very..." he struggled to find the word he wanted, "...British," he finished.

"It's a children's programme."

"Well then it should suit both of us," John retorted. "Anyway, I'm surprised you haven't been deleting them as we go along."

"I would love to," Sherlock replied. "But it's not practical while they are impacting your behaviour."

They walked on in silence for a while.

"So you managed to persuade Lestrade not to release the victim profile, that was good," John said.

"What?" Sherlock was deep in thought. "Oh, yes. Right. Wouldn't want to put the real killer off," he confirmed.

John stopped walking. "That's what you care about?" he asked. "You're not worried about copycats?"

"Hmm?" Sherlock realised that he had shed his companion and looked round. "Come along, John," he prompted. "You're the one who wanted to walk and now you're just standing about. How are your hands?" He took two steps back the way he'd come and pulled one of John's hands out of his pocket, tutting at the sight of it. "Stop giving your gloves to the homeless," he instructed.

"They look colder than I do," John replied, pulling his hand back and walking on.

Sherlock followed, glancing sideways at his set expression. "Oh, it's the 'c' word again." He sighed. "I shouldn't need to worry about that any more," he complained. "You care enough for at least a dozen ordinary people, so between us we're still ahead overall."

"You can't out-source your conscience," John told him stubbornly.

"I don't see why not," Sherlock replied. "I thought you'd be pleased. I listen to you, don't I? That's more than most people do with their consciences."

John said nothing, not sure how to respond to this new job title.

It would have taken John around an hour to walk home, going via Hyde Park and following the main roads. With Sherlock, you travelled more directly, popping out of side streets to find yourself much closer than expected and it was only forty-five minutes after setting off when they approached 221B, to find that they had a visitor.

Waiting on the front door step was Sally.

Sally, who had overcome her pride to ask for Sherlock's help in September, only to have it end in disaster, and who had been the driving force behind his ban.

Sally, who hadn't spoken a single word to him since that day, or stayed in his presence for a second longer than she could help.

Sally, who now raised her head as they approached and looked at Sherlock with distrustful eyes.

"We need to talk."