Author's note: Okay- I know these are getting longer. But…doing justice to both the current day story and the story of young Sherlock is proving to be very fertile ground for my imagination. Polonium is for Kate221b, although Part One takes it in an unexpected direction.

Polonium (Part One)

Po 84 atomic weight 209

Polonium is a radioactive, extremely rare semi-metal. It is reactive, silvery-gray, and it dissolves in dilute acids, but it is only slightly soluble in alkalis. It is fairly volatile, with a short half-life. It is easily dispersed into air- about half of a sample of it will evaporate within 3 days, unless it is kept in a sealed container.

"How are you doing in there?"

She put the whispered question gently, but she could see that it worried Sherlock nevertheless. He was trying not to fidget, but she saw the briefest flash of discomfort work its way into his eyes.

"The shirt itches, the jacket is too warm, the tie is…ridiculous-why do people put up with these things? The sun through that window is too bright in my eyes, the place reeks of wood polish and I would really rather be home right now."

It all came tumbling out at his usual breakneck speed, even if it was whispered. But, Esther Cohen was grateful for that. At least he's talking. She had worried that the 'pre-selection interview day' at Harrow would just prove to be too much and he'd retreat into silence. She'd worked too hard at making this happen, and she didn't want it to go wrong, for his sake. Of course, Mycroft had made it clear to his brother. Too clear- he scared Sherlock half to death.

"You need to take this seriously, Sherlock." Even 8,000 kilometres away and over a bad telephone line, Mycroft's voice carried weight and authority. "This is a one-and-only chance. You have to act normally, within acceptable bounds of behaviour. Lord knows, you've been taught enough of that by Mummy and your tutors. Now's the time to deliver the necessary performance. It's the only way you'll be able to avoid Father sending you off somewhere horrible. So, just…do it. I know you can, but it's time for you to prove to everyone else that you can, too, when it really matters."

Sherlock had been quiet, almost subdued into silence when she collected him this morning from the South Eaton Place townhouse. She spent the forty minute drive through north London's rush-hour traffic on last minute coaching and trying to get him animated. "So, Sherlock; the house master is almost certain to ask you why you want to go to Harrow. What are you going to say?"

The reply came back though slightly clenched jaw. "Because if I don't get into Harrow, Father will send me to a special needs school where I will be locked in, and then my brain will just shrivel up with boredom and I will want to die."

She sighed. "Not the answer I was looking for, Sherlock, and certainly not the one that will get you into Harrow. So, let's try this one again. Think of what they want to hear from you." The rest of the journey was spent polishing the rough edges off his reply.

Upon arrival at Harrow, it was straight into a computer-based intelligence test, and a composition writing test. Then they'd gone on a brief tour, which seemed to help settle him. They were now sitting in a small anteroom at Bradby's House*, waiting for the interview with the House Master. She tried to still her own nerves, hoping she would be able to mask her worries from those perceptive grey-green eyes. He looks fine on paper, but can he pull it off when he's face-to-face?

"Master Goodison will see you now, young man." The secretary at Bradby's was experienced at dealing with applicants. She kept her voice kindly. She'd seen boys pass out, burst into tears and once, literally run out of the room screaming. The interview was a nerve-wracking experience when so much of parents' expectations were riding on this one half-hour conversation.

Esther watched him go in. Good luck, Sherlock.

Geoffrey Goodison was a tall, thin, ascetic looking man, with dark hair and piercing eyes. He was standing and offered to shake hands with the thirteen year old, who hesitantly complied, with a not-too-hard, not-too-limp grip. The House Master thought, He's practiced that enough times to get it right. He gestured the boy into a hard-backed wooden chair in front of the desk and took his own seat behind the desk.

"You know it is unusual for Harrow to take an applicant this late. We only reserve seven places each year for late entry, across the whole school. This year I can only take one into Bradby's"

Sherlock nodded, as if not trusting his own voice.

"But, then you are unusual, and your circumstances are, too."

Again, the young boy nodded. His eyes were wandering about the study rather than looking at Goodison.

"So, Mister Holmes, tell me why you want to come to Harrow."

The boy seemed to hesitate. And then he raised his chin and said almost defiantly, "I've just seen your Chemistry labs; that's why I want to come here. They're BRILLIANT." The last word came out with a barely suppressed sigh of delight. "I'll be able to do experiments that I haven't been able to do at home…" Then as an afterthought, the boy pulled his eyes to the House Master's own and said belatedly, "…sir."

Doesn't like eye contact, but he'll do it because he's been told to do so, like that handshake. The House Master was used to boys being coached. He sometimes felt that the interview had become more a test of a boy's acting abilities more than a revelation of their true character. The last three late applicants he'd seen were certainly producing Oscar winning performances, probably because they'd failed their entrance interview at other public schools. As House Master, his job was to probe what was underneath the polished answers, to ask the unexpected, something that couldn't be predicted in advance, create a chance to see beyond the prepared speeches. This boy's answer wasn't polished, wasn't coached; it reeked of the truth.

Goodison had reviewed the boy's application, and the detailed reports from each of his tutors. Their praise was extraordinary, but then as educators paid by the boy's family to deliver the one-to-one tutoring of a boy schooled at home, their views could be …over-inflated, as a matter of self-interest. Parents who paid for that kind of teaching wanted to hear only the best. He needed to figure out the truth in the next thirty minutes. Certainly the intelligence test scores, already generated and on his desk while the boy was on the tour, boded well. They were the highest he'd seen in years. He scanned the boy's personal statement. A lot of it was about chemistry.

"You like chemistry, don't you?"

"Like?" A frown of confusion passed over the boy's face. "No, like doesn't begin to explain it."

That made Goodison smile. "Then explain it to me, please."

The boy looked down at his hands. "Chemistry is life. All life. It's how things become alive, and how when they die they revert to their basic elements again. It's about entropy and energy and how everything everywhere is connected. Everything else I've studied, well, if it helps explain the chemistry, then that makes it worth studying. I need advanced maths to work the equations, and physics to understand what is happening at the atomic level. But, the best thing is that chemistry doesn't lie. It's the essence of everything. The more I learn, the more there is to learn. I'm never bored with chemistry."

There was a passion and an intensity in the delivery of this soliloquy that made Goodison realise that he'd hit truth again. He decided to probe more; he needed to know how the boy's mind worked. "Tell me now what experiment you'd most like to do, if you could do anything at all."

"I'd like to find out why there's polonium 210 in cigarette smoke."

Goodison wasn't a chemist. He had a vague recollection that polonium was a radioactive element, but the idea that such a thing as found in cigarette smoke just sounded… preposterous.

"Is there?" it was a direct challenge. How would the boy take it?

Holmes tilted his head to the side a bit. There was a pause, when Goodison could see the war going on. Should he answer politely, or should he take up the challenge?

A little huff of breath, and then he was off. "Of course, there's polonium in cigarette smoke. That's been known since the 1960s, along with arsenic and cyanide, and other carcinogenic ingredients. But, the tobacco companies haven't exactly been shouting the results, have they? For obvious reasons, so if you haven't heard of it, then you aren't a chemist or a doctor. The scientific journals have the evidence though. Do you smoke?"

Goodison smiled again at the abruptness of the question. "Yes, occasionally. Have you tried it? Why are you interested in what's in it?"

Sherlock screwed up his face in disgust. "I couldn't smoke- the smell alone is revolting. My Father smokes. In part I want to know if the polonium will kill him, but really I want to know if it's a better way to produce polonium."

"What would you actually do in your experiment to test that?"

Sherlock looked uncomfortable, and his left thumb was rubbing his index finger fiercely. "Um, would you mind if I stood up? It will help me answer the question…sir"

It was unorthodox, but Goodison nodded; the boy was out of his seat in a flash and pacing.

"Polonium was first discovered by the Curies in 1898, but they needed to process over a tonne of pitchblend to yield a tiny amount of the element, just a hundred micrograms. If I could find a way to harvest it from cigarette smoke that would be a bit amazing. People make polonium now by blasting bismuth with neutrons. That takes energy. Tobacco leaves seem to accumulate the ingredients needed- don't know how, that's worth exploring in its own right. The hairy underside of the leaves seems to collect the raw materials from the atmosphere and soils. But what is really interesting is how that all comes together in the process of combustion through oxygen inhalation in the cigarette. Polonium is produced- but how? Would it work the same if the cigarette was much bigger- say the size of a brick? Is it because the tobacco is cured? Does that intensify the presence by driving off the water and other liquids? Is it because it is shredded? Would a brick-sized pile of tobacco leaves produce as much or more polonium if it was 'smoked'? It would be fun to design a machine to do that. And does it actually have to involve inhalation- which is after all just an intensification of oxygen flow? If you set a whole barn of fresh tobacco leaves on fire would it generate as much polonium? There are just so many directions to study." He paused to take a breath.

"You aren't interested in stopping people from smoking?" Goodison couldn't resist throwing a little grit into the machinery to see how the boy dealt with it.

The pacing stopped, and the head tilt reappeared. "Why would I want to do that?"

"Because saving lives is important?" The House Master volunteered this to see if the boy would revert to the coached approach to challenge. Almost everyone knew that one of the interview questions would be on ethics. It was an old standby for public school interviews.

"That's for other people, doctors and the like." The boy waved a thin bony hand in dismissal, and resumed pacing. "I'm interested in the chemistry. Having a sustainable, renewable source of polonium is really interesting. Instead of using tobacco to kill people through cancers…" here he looked pointedly over at the House Master, "why not harvest it as a source of a precious element? Only a hundred grams of polonium are manufactured a year- in the whole world. If there was more of it, then it could be used in scientific work that's really important."

Intrigued, Goodison tilted back in his chair, "Such as?"

The boy put his hands on the back of the chair in front of the desk, as if grounding himself. "Polonium 210 is an important source of neutrons. It's usually put together with beryllium, where the alpha particle emitted by the radioactive polonium helps in release of neutrons from beryllium. If that isn't enough, a small amount of polonium releases a large amount of energy every second in the form of alpha particles."

He clearly thought that was enough explanation. Goodison pursed his lips, and decided to call the boy's bluff, if it was one. "So what?"

That provoked a frown and undisguised criticism in the tone of the boy's reply. "If the pure science isn't good enough for you, sir, then think of the applications! It could be used in thermoelectric cells and in isotope thermoelectric generators, because that converts the energy released by the radioactive decay of an element into electricity. Think of space exploration; it could be driven by polonium if it was readily accessible and renewable through on-board hydroponics." The boy's direct eye contact was now directly challenging the House Master to realise the importance of his statement.

Caught up by the lad's enthusiasm, Goodison had to smile. Time to bring this back down to earth.

"You'd best sit down, Holmes. Harrow is much more than a chemistry lab. What about sport, the arts, music? What do you like doing when you aren't studying?"

The boy took his seat again, and stilled. "I play the violin."

Goodison tried to recall that fact from the application. "To what level?"

"ABRSM Level Seven distinction, sir."

For a thirteen year old, that was a significant talent. "Shame you couldn't have applied for a music scholarship here, but the auditions happened in February. Why do you like the violin- that is, assuming you do, and aren't just doing this to satisfy your parents."

"My mother taught me, to start with, but then she died. Father doesn't care. He only listens to my brother's piano playing."

"That doesn't answer the question."

"I like the violin because it's true. Music is like maths. If you can master the bowing technique and the fingering, then the sound is…perfect. I have a good ear, perfect pitch. And, like chemistry, if you put the basics together, you get something interesting. I like doing that. I like to experiment with it, write my own music."

As much as he was enjoying the conversation, it was time now for Goodison to focus on the principal question mark over this applicant. "You've been home schooled all your life. Not much contact then with boys your own age or older. There are a LOT of boys here at Harrow and a good deal of education here is about how to get on with each other. How do you think you'll do?" It wasn't meant as a trick question. He assumed the boy would have been coached in how to talk up his extra-curricular activities, his sociability. What came out was again blunt but honest.

"I don't know. I've not had a lot of experience with it. What I have had, with village boys near home, I didn't like much."

"Why?"

"Because they're stupid." He blurted it out, then went a bit pink, when he realised that it was far off line from what Esther Cohen had told him to say.

"Well, that's honest. But it won't endear others to you. Tell me about a friend of yours. What makes him a friend?"

"I don't have friends, at least not the way they write about friends in books."

"Why not?"

"I get bored with other people. I'm better on my own."

Goodison took a stern tone. "We don't often get that chance in life, Holmes. You need to learn how to get on with others- even the boring ones. A lot of Harrow's life involves activity outside of the classroom and we require you to learn teamwork and get on with others. It's important. If you don't want that, then Harrow is not for you."

"I know that I will have to get on with others. If the price of being here and using that lab is to learn how to deal with other people, then I will do it. That's what a school is for- to teach me what I don't know I need, in order to get what I want. That's why I'm here."

Goodison thought about that answer for a moment. Brutally transactional, not exactly orthodox. But, it was a basis on which he could work. And at least it was honest. He got up, walked to the door, and popped his head out. He asked "Would you like to join us now, Doctor Cohen?"

When the petite dark haired woman was seated, the House Master gave her a reassuring smile. "As you know, this is a late application, and an unusual one. Normally, at thirteen we'd expect a candidate to take the Common Entrance Exam, or the Common Academic Scholarship exams before applying. But Sherlock's GSCEs are a more than acceptable alternative in the seven subjects he took. In theory, his six As and a B would be good enough to get him into the Sixth Form here. But those boys are seventeen and eighteen years old. If he's going to get the best out of Harrow, then he will have to start as a shell* in September. We can adjust his academic work to the highest sets or a higher form where needed, but he will have to fit in with his age group for the rest of college life."

Esther tried to keep her delight off her face. And then a worry reappeared. "Is there any possibility of his coming into Bradby's this term? His home situation requires a move into boarding in the next two weeks."

Having made the decision, the House Master now realised that this boy was going to be a high maintenance choice. But, he thought it was worth it, just occasionally, to have a boy who wasn't so interested in having a posh public school name attached to his own. Holmes couldn't care less about Harrow's history, but that didn't matter. And if he wanted to start a term before the other new boys arrived, well, that could be accommodated. He decided to put Doctor Cohen out of her misery. She was clearly worried.

"It's unusual, but not unheard of. We have the space in the house- one of the international boys had to go back home in February, so there is a vacancy." Then he looked the boy in the eyes. "It could be useful to help you get used to a school environment, given that you've never had it before. We will want you to sit a couple more papers, too- where you don't have a GCSE- French, Greek, Latin for example. We will need to know how to slot you into the programme. And I will have the music master assess your violin-playing." He looked thoughtful for a moment. "It's workable, for the right boy. Of course, there are lots of bits to sort out but I see no reason why you can't get started this summer term. So long as you are prepared to give it a go, young man, I think we are." With that he stood up, and escorted them back into the anteroom. As they were about to leave, Esther gave Sherlock a rather pointed stare. He'd forgotten something important.

The thirteen year old realised his mistake and turned back to the House Master, to shake his hand. "Thank you, sir."

"You are welcome, young man."

"Um…sir, I really hope that you will consider giving up the smoking. Polonium 210 is radioactive, and sufficient exposure causes genetic mutations leading to cancer."

Goodison smiled. "I will bear that in mind, Holmes. See you in a few weeks."

oOo

John watched his agitated flatmate pacing. "Sherlock, really. I think you need to sit down."

That earned him a filthy glare. "You don't understand, John."

The doctor suppressed a smile. "Actually, I do. I've counselled enough people- friends, family and colleagues- through the process of quitting. It's not impossible. It just feels like it right now."

His flatmate huffed. "Well, the NHS website says that exercise is one way to stop cravings." He gestured at his legs, and resumed pacing.

John pursed his lips. "I think they had something else in mind, like taking up tennis or something. Your pacing is just winding you up even tighter. It's about using proper exercise to release endorphins. You've read the leaflets, you know that."

Sherlock groaned. He'd come to a halt in front of the mantle over the fireplace. He looked at himself in the mirror. His eyes were sunken and lacklustre, his face was flushed. "Just look at that- I'm a wreck. I can't concentrate on anything. I'm running a low fever. I'm exhausted but I can't sleep. My stomach hurts. I'm both nauseous and constipated. I've got a filthy headache. My chest hurts and I'm coughing. Look at this!" He held his shaking hand up for John to scrutinise. "This is NOT healthy, and if this is what it means to give up smoking, then I'm all for a relapse."

John tried to hide his smirk. In his most patient tone of voice, the one he reserved for the five year olds at the surgery who were in the midst of tantrums, the doctor just chided gently. "It's early days, Sherlock. How long has it been?"

"Six days, seven hours, twenty three minutes and a number of seconds. And every single one of those seconds has been counted, I can assure you. Surely by now I should be feeling better, not worse."

"I know you can do this, Sherlock. You've got a case of 'quitter's flu'. It will pass in another couple of days. You can wait it out. After all, you've managed to beat cocaine withdrawal, so this should be a piece of cake."

His flatmate just moaned again. He wrapped his silk dressing gown around his thin frame, strode back across the living room and sat down on the sofa. He clutched his head in his hands, tangling his fingers into the dark curls and pulling. "This is worse than a cocaine withdrawal. At least that is over quicker. This could take months, John, and I don't have time for it!" There was just the vaguest hint of hysteria in his tone. "I need some. I need some NOW."

Without another word, John got up and went into the kitchen returning with a glass of water, which he thrust at the heap of misery that was his flatmate.

The doctor in him had some sympathy with Sherlock's distress and agitation, even though, as someone forced to share his living space the process was proving to be very trying indeed. "You're just going through normal withdrawal. It won't kill you, so stop whining. Drink this; it's one of the D's"

That brought another filthy look from the sofa. "Whining? I am not whining, John. I am suffering!"

John tried again. "Think of something else. You've read it- another of the five D's is distract."

Sherlock sighed, but took the glass, grumbling "it will just make my stomach hurt more. It'll be your own fault if I throw up on you."

John tried to cheer him up. "One of the advantages of this is that you will get your appetite back, and you'll actually be able to taste food properly again."

The space between Sherlock's eyebrows wrinkled. "I'm hypersensitive, remember John? Why would I want to enhance my sense of taste or smell? As revolting as it was when I got started, the smell of cigarette smoke now just sets off a dopamine frenzy. I'm Pavlov's dog. Anyone lights up in the room and I start getting a rush."

When he put his empty glass down on the coffee table, he was still sulking. "It's no use. Without a case to distract me, the only thing I can think about is nicotine, smoking and the whole wonderful mysterious chemical reactions that should be firing up my brain's neurotransmitters. Instead there is nothing…No, I lie, it's worse than nothing. It's the absence of everything that I live and breathe for- mental stimulation, energy, pleasure- all those endorphines and adrenaline. Without a case, smoking is the only thing that keeps me sane."

"You've used nicotine patches for years; why are you saying now that it is impossible? I don't get that."

"I use both, John. I smoke and I use patches. If you think I can give up smoking and just rely on patches, then you don't understand how patches work. They are slow release- that means they don't actually work to do anything like what smoking does. A cigarette is the most efficient drug delivery system in the world. It crosses the brain-blood barrier and means that you get the full benefit in seven to ten seconds." He rolled up the sleeve of his dressing gown to reveal the two patches, gesturing dismissively. "This abomination drips a tiny dose through continuous osmosis across layers upon layers of epidermis. In short, it's designed to be ineffective background noise. I use a patch simply to keep my nicotine levels topped up to the point where a cigarette can send me into overdrive."

The doctor's patience was beginning to wear a little thin. "Maybe, but those patches won't kill you, whereas smoking will. So, just …I don't know …go meditate. Contemplate the statistics of avoidable deaths due to smoking, and try to imagine having to suffer the symptoms of chronic obstructive pulmonary disease. Let that fill your head with reasons not to smoke."

"That doesn't work. It never works. That stupid leaflet said I should beat cravings by going on a 'mini-mental vacation'. Have you ever heard anything so absurd in your life? I'm supposed to visualise myself 'well and happy in a place I cherish'." He snorted in derision "What utter rot! The only acceptable distraction is a crime scene. If I smoked there, Lestrade would shoot me, and Anderson would spend all his time berating me for contaminating the scene, instead of doing his job."

"For someone who's prided himself on his logic, you're not being very logical here. In fact, I'd say you're actually getting quite emotional about it."

Sherlock's glare now could burn holes through sheet metal. "I am not being emotional!" The volume and tone of voice in which the denial was uttered gave John all the proof he needed that his friend was just about to go into meltdown.

"Okaay, let's be scientific. What's in the smoke that you so desperately want to inhale?"

Sherlock was back up, pacing. "There are over 4,000 separate chemical compounds released when a cigarette is smoked, and most of them are toxic if they were to be ingested in sufficient quantities in one go- which of course, they aren't, so that renders the anti-smoking lobby almost apoplectic with rage. Carbon monoxide and nitrate oxides, of course- but you breathe those everyday as a pedestrian in London, so don't blame cigarettes. Then there's hydrogen cyanide. That's the principal ingredient of Zyklon B, a chemical used by Hitler in his mass genocide efforts- but again, in such trace amounts that a single cigarette isn't a matter of life or death. There's now evidence that there are at least three poisonous dinitroaniline pesticides used in tobacco farming that are being ingested through cigarette smoke-flumetralin, pendimethaliin and trifluralin. They are carcinogens, most cause oxidative stress and the last is an endocrine distrupter. Yes, over a lifetime of smoking this stuff accumulates. But…just one cigarette is not going to kill someone."

"Yeah, well, that's the problem isn't it? There is never 'just one' cigarette. The addiction means you just keep going back for more and more. What's the worst chemical ingredient in cigarette smoke?"

"Polonium 210."

"What's that?" John looked confused.

Sherlock waved his hand in dismay at his flatmate's ignorance. "I assumed, incorrectly it would appear, that medical school actually taught you something about the periodic table. No wonder the NHS is staffed by people who could write leaflets talking about 'mini mental vacations' as if it were real medicine."

John had a scale of Sherlockian insults that told him a lot about the mental state of his friend. That one was definitely starting to register in the red zone. Distraction therapy was needed, urgently.

"Okaay, for the mentally deficient amongst us normal people who don't know the four hundredth isotope of the 80th element on the table, explain why I should care about polonium."

This brought Sherlock to a halt. A confused look came over his face. "Number 80 is mercury and it only has seven isotopes." Then he started walking again. "Polonium, Number eighty four on the other hand, has the most number of isotopes of any element, which is thirty three, not four hundred."

John rolled his eyes at the little lecture. "So, what makes it worse than the other stuff in smoke?"

"All thirty three isotopes are radioactive, ranging in atomic weight between 122 and 220. Polonium 210 was used in the Manhattan project- with beryllium, it was a key component of the trigger mechanism for the Americans' "Fat Man" bomb used at Nagasaki. "

John's eyes widened. "Why isn't this better known?" He sounded incredulous. "I mean smokers are actually dragging radioactivity into their lungs?" His disbelief was palpable. "No wonder they make every packet carry a 'smoking kills' warning."

Sherlock just shrugged. "No one can prove that polonium is the guilty party…yet, anyway, but it is known that radioactivity leads to gene mutation- and carcinomas are just mutations, so yes, polonium is the prime suspect. "

John fixed him with an outraged stare. "You claim to be a chemist but you are willing to put that…that stuff into you? I don't get it. How could you?"

"Well, I don't think of it in those terms, do I? Smoking is a means to an end- the adrenaline rush, the stimulation that I need to clear a path through all the sensory input- you don't really understand it, John. it's a case of 'Live today, for tomorrow I may die'. I need to smoke now in order to stay sane under the onslaught of just so much data. It's a form of self-medication."

John narrowed his eyes at the direction this was going. It was as if Sherlock was talking himself back into smoking. "What's the half-life of polonium 210?" he barked.

"138.376 days"

"Well, I don't intend to be there watching you go through chemotherapy when your smoking causes cancer. So, every time you even think of smoking in the future, just calculate the half-life decay of your blessed polonium and work it through mathematically through every single step of decay. If you still feel cravings after that, then just…" he hesitated a moment. "…then just go on a little mini mental vacation exploring the periodic table for another lethal chemical you want to avoid."

Author's Note: To all you smokers out there, I'm not going to apologise. My mum died of COPD this year, and my sister has also got it. Both smoked. Just stop now.

* At Harrow, the 800 plus boys live in one of twelve houses, and the masters of each house have the deciding vote on admissions. Bradbys is one of the smaller houses, home to seventy boys across the five years that most students are at the school. First year boys- usually 13 years old- are called "Shells". The next year is called "Remove", the next is the more conventional "fifth form", followed by the final "sixth form" years.