Author's Note- apologies for the week long delay. I have been working on another story that I will start posting next week, called Musgrave Blaze. Now that it is 20,000 words along, I am able to juggle it with Periodic Tales again.

Chapter Twenty

Sulphur S 16

A non-metallic mineral, elemental sulphur is a bright yellow crystalline when at room temperature. Disulfide compounds are largely responsible for the mechanical strength of the protein keratin, found in the outer layer of skin, hair and feathers, and the element contributes to their pungent odour when burned.

John was tired, worn out, knackered. It had been a brute of a day at the clinic. The annual "Flu jab-a–thon". They'd seen over 200 patients, with three doctors and nurses taking a continuous stream of elderly patients through the process. Like a factory assembly line, the receptionist ticked off names, handed them numbers in sequence printed on yellow, green or blue tickets that people normally associated with raffle prizes. John drew the blue tickets- and he swore that the nurse had it in for him, and gave out blue tickets to every awkward, cantankerous old fool she got through the clinic door. He was certain that his dreams would be filled with the explanation of what the jab did to protect the elderly person; he certainly knew the patter as well as a stage actor knew their lines.

The only variation to the routine occurred when on three occasions a patient queuing in the blue line fell over. Two were just old and doddery, and found standing for so long hard. Another passed out, giving John a welcome chance to use his diagnostic skills rather than his injection technique. A simple case of low blood sugar, easily remedied with a carton of orange juice and a biscuit.

So, the last thing he wanted was any drama on the home front. A nice cup of tea, a take-away meal, crap telly and a warm bed- in that order, no deviation.

But by the time he'd taken his second step from the front door onto Baker Street, he knew his chances of that were slim in the extreme. Mrs Hudson greeted him in the hallway with a pained expression. "John, you really need to tell him to stop this sort of experiment. I mean, just take a sniff!"

He didn't need her admonishment; he could smell the problem from the moment he crossed the threshold. The most revolting combination of rotten eggs and burning hair was coming down the stairs from the flat.

"I've opened all the windows in my flat- it's freezing! I had Mrs Turner over for tea, and she had the nerve to complain about the smell, saying her lodgers never did anything like this."

John went up the stairs and gingerly pushed open the door into the flat. He swallowed the bile that threatened to come up his throat; it really was the most nauseating scent he'd come across- even a badly decomposed body at Barts managed to be more tolerable than this. Was it his imagination, or was there a haze of…something that made the air seem murky as well as smell disgusting?

He noticed that both windows overlooking Baker Street were wide open. Turning back to the kitchen, he saw an extraordinary sight. To start with, Sherlock was virtually naked- just wearing underpants, goggles and…was that a set of nose-plugs? John was used to his flatmate's mad scientist days, but this just took the biscuit, especially since it was so cold in the flat that his breath clouded. He watched as Sherlock touched the blue flame of a blowtorch to a sample of…something stretched between metal clips on a table-top scaffold.

Instantly, the stretchy piece of what looked like leather scorched, charred and then emitted smoke. A waft of something even more revolting reached John's nose, which was actually beginning to hurt.

The doctor lost his temper. "Sherlock! What the fuck are you doing? I thought you were the one with the hypersensitive sense of smell!? How can you just stand there when that is just so revolting?"

"I'm comparing the odoriferous nature of sulphur reduction compared to sulphur combustion." This was uttered in a most peculiarly nasal sounding baritone, the effect of the nose plug.

While John digested Sherlock's bland statement, he had to ask. "You must be freezing. Why are you…um..naked?"

"I'm not. As you can well see, I am wearing pants in deference to what others would think of as decency, although to be honest it is a nuisance, because I will have to throw them away. The natural fibres in my clothing will retain the scent, even after washing. My skin and hair will not."

John looked around at the room. "Well, that's you sorted, but what about the rest of the flat?"

"As Mrs Hudson's concept of carpet, curtains and soft furnishings have a high proportion of man-made fibres, the scent will dissipate within a couple of hours." The brunet turned off the blow torch and then bent over the kitchen table, putting his nose close to the now blackened specimen. He took a breath, and then removed his nose plugs. John watched as the man's face twitched, his eyes started to water and his features took on a look of disgust.

"If you don't need those nose plugs, I'll have them." John tried to keep his voice calm, but it was difficult. Without a word, Sherlock handed him the beige plastic swimmer's equipment.

Now John was the one with the nasal twang. "Just what is all this in aid of?" Even to his ears, his voice sounded like some sort of cartoon character.

"Case, John. I wouldn't willingly be doing this if someone's alibi didn't require it. Should be done with this phase in a couple of minutes."

"Right, then. I will just have to make myself scarce for a while."

"The fumes are heavier than air, John. Your bedroom upstairs will be much better, and your nose will give up after a while- nasal receptors get overloaded and shut down. That's why I need the nose plugs back; I need to be able to smell these, and distinguish between them. So I have to wait fifteen minutes between tests for the sense of smell to return."

Reluctantly, the doctor pulled the plugs from his nose, and started to head into the hall. Anything to get away from the smell. He couldn't face having to stand in the kitchen long enough to make himself a cup of tea. But, he thought he might grab a glass of milk. He went around the eccentric scientist, eying the charred remains. "What is it?"

"You don't want to know; really, John." The doctor decided to take his word for it. Sherlock was writing something in his notebook, as John reached the fridge and started to open the door. As he did so, Sherlock said. "I wouldn't do that, if I were you." The nose plugs were back on and it sounded weirder than ever.

The connection between John's brain and his hand seemed to have been slowed by the stink of the experiment, and impulsion kept him going as he tried to understand his flatmate's warning. The door of the fridge was open by the time he realised it was too late. What came out of the fridge made John actually gag in revulsion. It was the most disgusting scent that John had ever come across. He slammed the door shut and turned back to his flatmate. In a voice tinged with horror, he asked "What died?"

Sherlock smirked. "Nothing. If it had, you'd be smelling putrescene or cadaverine. That scent in there is something entirely different from decomposition, John." He wrinkled his nose; "I can't talk and breathe through my mouth at the same time." He pulled the nose plugs off again. " What's going on in the fridge is sulphur reduction- what happens when bacterial enzymes digest a wide variety of foodstuffs. This one is cabbage mostly, leavened with onion, garlic and chive, a handful of Brussels sprouts and one of cashew nuts. The recipe is simple- just add e coli bacteria and voila- think of the result as what goes on in your digestive tract. It releases hydrogen sulphide, amongst other trace sulphur compounds."

"Sherlock, whatever is going on in that fridge smells like shit."

"Well, yes, of course it does. That's what happens in your gut. Didn't you learn anything in medical school? I'm not interested in the indole and scatole released, just the sulphur. A lot of the sulphur compounds are volatile, and emerge as flatus or bad breath. What you are smelling in the fridge is methyl mercaptan, reputably the world's smelliest molecule, and a key ingredient of excrement."

John stifled a giggled. "I've heard Lestrade complain about shit cases before, but, what does shit have to do with a case?"

Sherlock looked up, his puzzlement clear through the goggles. "Who said anything about a case involving shit? I am interested in the methyl mercaptan- that's CH(4)S. Although it's a natural substance found in the blood, brain and other tissues of animals and people, it's toxic in sufficient quantities. It binds to cell membranes, and the iron in enzymes with haem- so it messes up human respiration and inhibits mitochondrial electron transfer. Hydrogen sulphide causes respiratory distress," here he gestured at the still smoking specimen, "but exposure for only a few minutes to high concentrations of methyl mercaptan can kill within forty five minutes because it destroys both respiration and liver function." The detective smirked, "In short, John, what's in the fridge will kill you before what's in the air."

"And why are we dicing with death, Sherlock?"

The brunet gave an involuntary shiver; with the windows wide open, it was cold in the flat. "The case, John. A woman has been murdered, but there is no trace of a wound. Cause of death is acute respiratory distress and liver failure. The medical pathologist has said that she died of complications from her cancer treatment interacting with sulphur fumes. Anderson made up some daft excuse to explain the traces of burned sulphur residue in the greenhouse where she died, saying she was trying to kill off powdery mildew fungus. I think that was a smokescreen set up by the murderer."

He sniffed again at the specimen. "The other people on the crime scene didn't smell what I did- which was a trace of methyl mercaptan, rather than sulphur dioxide."

"If it smells like what's in the fridge, how the hell could anyone be stupid enough to eat or drink something laced with it?"

""Use your imagination, John. Inside a syringe, you wouldn't be able to smell it. She was being treated for ovarian cancer and making a good recovery. I think her husband decided he'd rather she died, so managed to introduce a dose of methyl mecaptan into her intraperitoneal injection site. It would have been absorbed by the mesentery veins and then gathered into the portal vein of the liver. The husband is a chemist working in the petrochemical industry and he would know the effects of the compound. So I am trying to see if it is possible to grow my own methyl captan in sufficient concentration. That fact, plus opportunity and his obvious motive should be enough to convince the coroner to give an open verdict or, better still, declare it as unlawful death."

The doctor thought about the lengths to which Sherlock was willing to go to prove his case. "Tell me that you will thoroughly decontaminate, sterilise and deodorise the fridge as soon as you are done."

"Of course, John. I am hypersensitive to scent, so am even more highly motivated than you are to finish this."

"Well, hurry up and get some clothes on before you catch your death of a cold or flu."

Sherlock rolled his eyes. "Given what you've been doing all day, doctor, you are more likely to have been exposed to influenza germs than me. Besides, I defy any flu-ridden person to come within a couple of meters of me at the moment. The smell alone gives me protection." He unclipped the specimen from the scaffold and waved in front of the doctor, as is warding off evil. John laughed at the absurdity of the scene, but realised that, as usual, his flatmate was right.

oOo

Esther Cohen's shift had been a long one, and she closed her locker door at Royal Bethlam Hospital with a sigh of relief. She leaned her forehead against the cool metal and closed her eyes for a moment. One case after another- starting with a sixteen year old boy high on drugs and screaming his lungs out. He had resisted arrest, attacked the police officer, biting him so hard that it not only bled but nearly broke the man's finger. He was still screaming obscenities as they brought him in, handcuffed and taped down to the ambulance back board- not because of any injury, just to protect the rig's crew from being attacked. Sixteen was young for schizophrenia, but all the signs were there.

Hallucinating teenagers were hard to talk to, even after narcan and sedation, but the next patient had been even harder- a three year old boy, showing signs of physical abuse showed up at the Emergency Department. She loathed that sort of case- arguing with parents, either of whom could be the perpetrator, negotiating with social services to take the child into care, and notifying the police. The paperwork alone was a nightmare, when all she really wanted to do was deal with the pitiful results- a bruised and battered toddler, who wasn't willing to talk.

Those cases, as stressful as they were, did not upset her as much as the last one, however. She was literally half way out the door after clocking off when the ambulance arrived. A young girl had been found wandering in a park in Beckenham, naked but covered in excrement and blood. Esther had been called in to help restrain her, and ended up covered in the mess, too. She reeked, but a shower would have to wait, because whenever the nurses tried to wash the patient, she started screaming. The young girl was hysterical with fear, to the point where she wouldn't tell a soul her name.

Eventually after two hours of patient work, Esther had pieced together the story. Amina had just started her periods and had been dragged by a group of Asian boys into a back alley. They called her a slut and unclean, and then ripped her clothes off and covered her in dog shit. She had wet herself, thinking they were going to kill her, but they just beat her up instead. Her crime? She had been seen in the park talking to one of the neighbours- a white teenager. "They said I was a stain on the honour of the community. I was shit, I had to smell of shit; they forced me to eat it, too." By the end of the session, Esther had calmed the child down enough to be touched. To demonstrate that there was nothing to be ashamed of, Esther had cuddled the child and got her to agree to take a shower by herself. When Amina took the offered tablets and drifted off to sleep, Esther gave a sigh of relief. She'd be back in eight hours to start the process of treating her; in the meantime, photographs were being circulated by the police in the hope of someone coming forward to identify her.

All in, the thirty six hours on duty and on call had taken a toll on her sense of well-being. It was days –and nights- like these when she began to think that paediatric psychiatry might not be where she wanted to end up in her medical career. She stank of shit and blood herself, but rather than clean up and change at the hospital, all she wanted was to go home. At least on the bike ride to her flat she would not offend anyone- public transport was impossible when she smelled like this. She pedalled up the tree-lined Monks Orchard Road, around the roundabout and then on up South Eden Park Road, turning right onto Cresswell Drive. Her flat was in Osborne House, where most of the occupants worked in the nearby Langley Court Research Laboratories. The studio apartment was all she could afford, but she preferred it to a larger one which would have meant a flat-share.

She threw her keys onto the tiny hall table and hung up her coat on the wall rack, then kicked off her shoes as she walked down the corridor between the galley kitchen and her bathroom. She started unbuttoning her blouse as she walked; that shower was going to be extremely welcome.

Her hand fumbled the button as she realised that there was a man standing at the window, looking out across the parkland. The idea of a stranger in her flat just made her brain seize up for a moment, then she was frantically re-buttoning her shirt and backpedalling towards the phone that was also on the hall table.

"There is no need for alarm, Doctor Cohen. I am not a burglar or a stalker, just someone who wants a professional opinion." There was something in his confident baritone that made her hesitate before she picked up the phone. The man's voice was deep, but calm. No, somewhat curious, too, as if he was slightly bemused. She stared at him, trying to identify him. He was tall, well-built but tending towards heavy now that he was middle-aged, with reddish-brown hair. For a moment, she wondered if she'd seen him before somewhere, perhaps the parent of a patient at the hospital? She hoped not- as today's cases showed, parents were not always on the side of the children she treated, and he could be seeking revenge for her role in taking a child into care.

"Who are you?" She pulled the handset from its cradle, punched in the emergency numbers and held her finger poised to hit dial.

"I'm Richard Holmes, and I've been wanting to speak to you for some time about one of your patients."

Of course. Now that she had the connection, she could see the similarities with Mycroft Holmes. But she saw nothing of Sherlock in his features. She put the phone back down, and returned to face the man. With her hands on her hips, she glared at him. "How the hell did you get in here?"

"That's irrelevant, Doctor. It's a bit more seemly than being seen loitering outside in the hall. Your neighbours would be suspicious."

"Damn right and for good reason. So, why didn't you do what most normal people do- telephone, make an appointment at the hospital, or have the courtesy to write a letter?" She might be small and a lot younger than he was, but she was angry enough at his intrusion to make up for it.

He looked bemused at her posturing. "None of those approaches would have told me even a fraction of what this place tells me about you. And, given your role as my son's psychiatrist, I find it useful to know more about you than can be gathered from professional credentials. For example, the fact that your current work is rather hands on, if the stench you are emitting is that of a patient rather than some unfortunate personal accident."

She wanted to kick him out. She found his attitude atrocious and just a tad threatening. But, there was a little thought kicking around in her head- this might be the best opportunity to find out just who this guy really is, and why he has had such a toxic effect on both his sons.

"Sit down." It was an order, and she wanted to know if he would be sensible enough to give her some degree of control. If not, then she would chuck him out. He cocked his head at her tone, and gave her the slightest smile. That broadened as he chose her favourite chair and sat down.

Okay, you want to play mind games with me, Mr Holmes? She turned her back on him and went into the galley kitchen, filling the kettle and switching it on. He could wait. She was going to have a cup of tea and let him be damned. While the tea bag steeped, she went into the bathroom, stripped off her outer clothing and stuffed them into a plastic bag which she tied up. No need to make everything in the hamper smell. Then she pulled on her long fluffy bathrobe. Collecting her cup of tea, then, and only then, did she return to the living room to sit down on the sofa, all the while making it clear that she was not getting him anything to drink. She watched him watching her. She said nothing, waiting for him to start.

His eyes reminded her of Mycroft- hard and very determined. Just as he drew breath to start speaking, she interrupted. "He takes after you."

The eyes grew even colder. "I presume you mean my elder son. There is nothing of me in the younger."

"Oh, he's not legitimate then? Did your wife have an affair?" She said it as offhand as she could manage.

A muscle in his jaw tightened, but he did not rise to the bait. "No, DNA does not lie. Genetically speaking, he should have been perfect, but something failed between blueprint and actual production. A manufacturing defect- statistically speaking, they do happen, even with the best designs."

His cold-bloodedness made her almost flinch; how callous could a parent get about an autistic child?

He continued, "What has Mycroft told you about Sherlock's behavioural disorders?"

"He hasn't had to tell me much; I've had access to your youngest son's medical records, and I've seen Sherlock. Mycroft let me form my own diagnosis, rather than trying to prejudice me."

Richard Holmes had a commanding presence, even when seated he exuded a confident power- the authority of a man who was used to leading, one who expected obedience. He didn't like the quiet criticism in Esther's tone.

"You've seen Sherlock on three occasions. Twice at that geriatric facility your uncle runs- oh yes, I did manage to track down where you hid him. And then for a more extended period when you spent four days at my home. A waste of your time; I do hope you weren't charging Mycroft by the hour. He can be rather naïve about such things, but then he is young and inexperienced when it comes to procuring medical support for a defective child." Everything in that sentence was designed to make clear his disapproval.

She needed to nip that in the bud. "Mr Holmes, I am not contracted to you, and, to be blunt, what you think about my involvement in Sherlock's treatment doesn't matter."

He smirked and held up his hands in mock surrender. "I am not here to quarrel, Doctor Cohen, just to understand. In less than a month, Mycroft returns to Oxford. Quite pragmatically, he is negotiating what will happen to his brother's care when he resumes his studies and leaves the boy behind. I have already pointed out to him that he cannot legally stop me from returning to my home in Sussex. I have been willing to spend the summer at the London townhouse, but that's a temporary measure. My business interests involve corporate hospitality at the larger house. I have tried to convince Mycroft that the best solution for Sherlock is an institution capable of meeting his needs- a special school that can deal with children of his kind- but he insists that the boy should remain in familiar surroundings. Mycroft has spent the last month putting in place a series of carers and tutors, people who will keep the child occupied."

He leaned forward in the chair to scrutinise her more intently. "You are one of those people, so forgive me, but I am a little curious to know more about you, and why Mycroft thinks you will succeed any better than the shockingly large number of other medical professionals who have tried in the past. My wife, you see, used to think that the boy could be 'fixed' somehow. I told her it was hopeless and a waste of her time, but alas she saw things differently. It cost her health and her happiness, and eventually, her life."

Esther sipped her tea. Mycroft had discussed the arrangement with her. She agreed that after such a lengthy stay in an institution, Sherlock needed familiar territory, even if it meant being near his father. "I have no doubt that Sherlock will do his level best to stay out of your way, Mr Holmes. By what I was able to observe during my visit, he has developed a large number of avoidance strategies that work remarkably well. By the way, you may be surprised that for someone diagnosed as autistic, who shouldn't be able to understand emotions very well, Sherlock believes that you hate him."

The man snorted in derision. "I don't hate him, Doctor Cohen. I don't care enough to waste that level of emotion on him. The boy mistakes neglect for concern. It is said that autistics are unable to form emotional attachments; well, it works the other way, too. It is nigh on impossible to form a productive emotional relationship with someone like Sherlock, so I have never attempted it."

He said this with no malice, in just a pragmatic tone. "The house is large enough that our paths won't cross. He will have the freedom of the west wing, and the house and grounds when there is no one visiting me. I tend to be away a lot on business trips. He has become rather good over the years at avoiding me, and I certainly do not seek his company. Mycroft knows it will work, because he knows both me and his brother."

She put her empty cup down on the coffee table. "Why does it matter what Mycroft thinks of the arrangement?"

That provoked a slight smile. "Because he is my son and heir. He is Lord Mycroft, Viscount of Sherrinford, and he will go far in this world. Don't take my word for it, lest you think I am being a doting father. His tutors at Eton and Oxford are just as sure as I am about his promise. I would not have Sherlock come between us. He isn't worth it. So, I have waved the white flag of surrender. If Mycroft thinks he is being noble, doing the right thing by his little brother, then I cannot change that idea. I don't really have to do anything but wait. Sooner or later, Mycroft will come to realise Sherlock's limitations, and that he is a burden that need not be borne. Then he will shut him away and get on with his life. My elder son is certainly no fool. Time will come when he will put away sentimental loyalties."

The man got to his feet gracefully. Aware of his towering height compared to her sitting on the sofa, she stood up, too.

"So, by all means, Doctor Cohen, do whatever you think is best. Please forgive me if I think it unlikely that you will be able to help. You are a paediatric psychiatrist with no private practice experience, whose work to date consists of hospital consultations with patients you rarely if ever see again and whom you cannot possibly treat through any consistent therapy. Your academic research was well-respected at Oxford, but Sherlock is not some ordinary child who can be talked out of misbehaving. You won't be able to 'fix' him, Doctor Cohen. He's not fixable."

He started for the door. "I won't thank you for your hospitality, Doctor Cohen, as my unorthodox entry made you forget your manners. It is possible that we might bump into each other at the house in Surrey, where I will try not to reciprocate. Until then, I will say goodbye."

Patronising bastard. Not for the first time, Esther Cohen realised that helping Sherlock was something she really, really wanted to do. Not just for the boy's sake, nor for Mycroft's, but now she realised what a personal pleasure it would be to make Richard Holmes learn just how wrong he was. She headed for the shower; she had an overwhelming need to feel clean again.

Please review. After days without input (yes, I KNOW it's my fault for not posting!) I am in need of feedback.