Authors note:

I'm hoping that I don't manage to blind you all with medical science in this chapter and that the story will carry the technical details through! There are some explanatory notes at the end, but as ever if there's anything else you want explained then please let me know.

Hope it was worth the wait!

James MacPherson listened to what John had to say and offered to do the transoesophageal echocardiogram himself that afternoon. John didn't know whether to be relieved or horrified when he saw the vegetation on Sherlock's tricuspid valve appear on the screen. Molly had been right and they had found the cause. The flow through the valve itself was disrupted, the valve leaflets failing to close properly when the right ventricle contracted, resulting in a torrent of blood flowing back into the right atrium as the ventricle contracted rather than all of the blood being forced into the pulmonary artery and through the lungs, as it would with a competent valve. That regurgitation of blood with each cardiac contraction had caused the murmur that John had heard when he had listened to Sherlock's heart.

John had relayed Molly's theory about the possibility of a fungal infection in addition to the presumed bacterial one and following the echo results, James had written Sherlock up for amphotericin B, a powerful anti-fungal drug which was the treatment of choice for fungal endocarditis.

'So what now, does he need surgery? Will that fix it?' John asked.

'I'll get my cardiology colleagues to come and see him,' James Macpherson said, 'but I'd keep surgery as a last resort.'

'But Molly said he could do without the valve. Surely you'd be better to remove the source of infection? It doesn't look as if it's doing him much good with that degree of regurgitation anyway.'

''It's major cardiac surgery, John. I'm not sure that we could get him through it. His kidneys are hovering on the edge of failing as it is, and a period on bypass could just push them over the edge,'

'Then haemofilter him first,' John said, referring to the use of a machine to effectively replace the function of the kidneys.

But James Macpherson shook his head. 'That's not the only issue. The bottom line is, I'm not sure that any of him could withstand further surgery at the moment. I don't think we'd get his heart restarted after bypass. If he goes into overt cardiac failure then we won't have a choice, but his chances of surviving surgery would be slim.'

It was a stark, honest reply. If they tried surgery, then Sherlock would probably die. If they didn't try surgery, then he might well die anyway. John sank onto the chair next to the bed, head in hands.

'I'm sorry, John,' James MacPherson said, placing a hand on John's shoulder. 'He still has a chance, but it's getting slimmer by the day. Antifungals and a switch in antibiotics are our best hope now. Is there anyone I can call for you? Your wife?'

John shook his head. 'Things with Mary - they're not so good at the moment. I'll call Mycroft in a moment, he'll want to come and see him.'

What he couldn't say to James was that Mary was the last person that he wanted to see. He had compartmentalised this, as he always did in difficult situations, and Mary and his relationship with her, Mary and the child that she was carrying, they were objects from another existence that he could not contemplate until this was over. His world at this point in time was Sherlock, and this unit, and doing whatever it took to keep him alive, even if that possibility was looking less likely by the day.

'How about somebody to support you?' James was asking. 'You've been here day and night since he was re-admitted.'

John shook his head again, 'I'll be fine. I just want to be here for Sherlock.'

What was it that Sherlock used to say? 'Alone protects me?' John was finally starting to understand what he meant. If he had to discuss this with anyone at the moment, if anyone asked him how he felt, then all of his resolve, all of his strength would fall away, and he couldn't risk that. The nurses were kind, but efficient and business-like. They were there to care for Sherlock, for the many pumps and machine keeping him alive, turning one down and another one up, suctioning the numerous tubes, turning him and washing him, writing down line upon line of figures, taking samples from his arterial line and his central line, changing over bags of fluid and syringes of medication. They were courteous to John, and would occasionally suggest that he go off and get a coffee to enable them to perform more intimate procedures, or the night staff might suggest that he go and get some sleep, but it was clear that Sherlock was their patient and not John. Their conversation with him was polite, but if he didn't want to talk then they were happy to allow him to sit in silence, where those who knew him better might well not have been.

Alone, he could push emotion out of his mind and concentrate on the patient before him, on using all of his will to keep Sherlock alive. Magical thinking. He knew exactly what he was doing, and he knew how illogical it was, but concentrating on that was far preferable to contemplating all of the other issues outside this room that he would have to address when this was all over. 'When Sherlock is better' he told himself firmly, because the alternative was simply too horrible to contemplate.

...

The amphotericin was started within an hour of the echo to treat the presumed fungal infection. All that John could do now was to hope and pray that it would work.

Of Mycroft there was no sign. Anthea told John that he was abroad, on business, and could not be contacted. John knew exactly what that meant; he was doing something so classified that not even a dying sibling would be reason enough to extract him. Before his departure on his trip, Mycroft had left strict instructions with Anthea that Sherlock's parents were not to be contacted either, except in the event of his death. It turned out that Sherlock had left a living will filed with his solicitor which said the same thing. He didn't want his parents at his sick bed, or even at his death bed. So no Mycroft, and no Mr and Mrs Holmes. John was in this on his own.

For the next few days, things looked grim. Sherlock's renal function deteriorated on the amphotericin and they started haemodialysis, using a machine to continuously filter his blood, taking over the function of his failing kidneys. Despite the treatment, Sherlock's lungs started to fill up with fluid, and frothy pink sputum was coming up from the endotracheal tube, a sign of worsening right sided heart failure. A frusemide infusion was started to try to drive off the excess fluid, together with levosimendan to attempt to improve his cardiac function. Much to John's dismay, the cardiologists agreed with James MacPherson's reluctance to operate, and were even more emphatic. Whatever happened, surgery wasn't an option, not during the acute phase of his illness anyway. For now, it was antibiotics and antifungals or nothing.

John was counting the organs that were failing: failing lungs, their function replaced by the ventilator; failing kidneys replaced by the haemofiltration machine; failing heart supported by the inotropes being pumped into Sherlock via the central line; even his liver was gradually giving up the ghost as it was slowly poisoned by the amphotericin. Three organ failure, with an option on a fourth. What was the survival rate from that? John decided that he would rather not consult Doctor Google on this one. Sometimes it was better not to know.

His phone had rung and beeped almost constantly for the first few days, or rather buzzed and then flashed up with missed calls as he had turned it to silent. Mary had taken to phoning every hour on the hour, but he had found it surprisingly easy to ignore her calls. At some point, tired of jumping every time somebody walked into the room, convinced that it would be here and unwilling to face a discussion with her, he had texted her. Asking her to stay away; telling her that Sherlock was critically ill, and that all that he could think about at the moment was that, and that until he knew if he would live or die, he could not even contemplate anything else. Compartmentalising. A skill learnt from years of working as a doctor, when no matter what the arguments or the heartbreak outside the doors of the hospital, you learnt to switch off that area of your brain where you walked through the doors of the hospital, to put your 'real' life outside those walls aside, because your patients wanted their doctors to be human, but not too human. The only tragedy within those walls could be theirs. And now it was Sherlock's, and perhaps John's.

Mary, to her credit, stayed away, although John's phone still buzzed almost constantly. Eventually, the battery ran out and he felt no urge to rush to charge it. His iPad enabled him to do the constant trawling though the internet to look for new drugs, new treatments, new ideas, anything that might save Sherlock. He had even suggested a ballon pump at one point, to aid Sherlock's failing heart, but like all of his ideas, that had been met with a shake of the head and a calm explanation by James MacPherson and the intensivists that Sherlock's failure was all right-sided, and a balloon pump would be unlikely to help where the inotropes couldn't.

Being a relative was hard, but being a medical one was doubly so. The sense of uselessness was immense, and the hours stretched long beyond the number that it should be possible to have in a single day. John sat, holding Sherlock's hand, talking to him in the vain hope that he could hear him. Talking to him about something, anything to keep him fighting. Lestrade visited a couple of times, both briefly, obviously uncomfortable in the strange environment of ITU, unable to find a way to talk to a Sherlock so utterly silent and compliant, and he had made his excuses and left within ten minutes on both occasions.

Molly's cultures came back as negative initially, but she told John that fungi could take up to four weeks to grow. In the meantime she was still waiting for the results from the PCR test, which she hoped would identify the organism. She had other less clinically relevant results for John, however, when she came to visit the following evening. 'I did some more tests on the central line,' she told him. 'There were traces of ketamine on it.'

'That's an anaesthetic drug though. They could have used that here.'

'I checked his records, they didn't. I'm sorry, John.'

John hesitated, weighing up the implications of what she was saying; remembering the mould spores that she had found in the line, and her theory about where they had come from. 'So what, you think that he administered it himself? Before Leinster Gardens?' he asked.

'I found traces of ketamine under his fingernails as well. I think that's exactly what he did,' Molly said. 'The line also tested positive for diamorphine, and what looks like citric acid, as well as the morphine and fentanyl that he was given here.'

John remembered the paramedic struggling to find a vein to cannulate after Sherlock's collapse in 221b. Remembered looking himself and finding them all thrombosed, and then his jubilation at realising that the central line was still in place. The temptation for Sherlock, desperate for something to numb the pain of his injuries must have been irresistible.

But had Sherlock - careful, meticulous, Sherlock Holmes, really injected a syringe full of potentially infected drugs into a central line going almost directly to his heart? Surely he wouldn't have been that reckless?

And then John thought of 221b, of the chemicals left all over the kitchen table and the eyeballs and severed fingers kept in the fridge. Of course he would. He wouldn't see the danger of infection: he would only see the problems of being in pain, the craving to get high, and the solution - the rapid access to his own vascular system, unrestrained by thrombosed veins and shaking hands. Of course he had used the central line. It had been the logical solution. And Sherlock Holmes would always bow to logic above all else.

John groaned, wondering how deep into this thing Sherlock was. Because if he had been desperate enough to inject into his central line, then that spoke into a deep and entrenched addiction that not even a prolonged period of time in hospital was going to address. It might prevent him from using, might solve his physiological and pharmacological addiction, but the psychology of his addiction would remain unchanged. John was going to have to get him to accept psychological help. How, he had absolutely no idea. He looked over at Sherlock as he lay motionless on the white hospital sheets. The only sounds in the room were the sibilant wheeze of the ventilator, the hum of the haemodialysis machine, and the odd puff of air from the self-inflating bed that had become John's constant soundtrack over the last few days.

Sherlock was attached to a seemingly endless number of tubes and wires, monitoring him and keeping him alive: central line, peripheral line, arterial line, endotracheal tube, nasogastric tube, urinary catheter, dialysis catheter, ECG monitoring leads. John could count eight different substances currently being poured or dripped into his body, the most recent the bag of red cells that had been put up to correct his resistant anaemia - a product both of the constant trickle of blood into his chest drain which showed no sign of abating, now that his clotting was deranged by the sepsis, the effects of the amphotericin, and the multiple blood tests that were being taken every day. John wondered how many units of blood he'd had since his illness - more than twenty, less than thirty he would guess. And not just red cells but all the other components too - platelets and plasma and even additional clotting factors. So if all of Sherlock's own blood had been replaced not once but many times, was there anything left that was still his own, and if so how much of him was still Sherlock and how much was a stranger?

John mentally shook himself, and reached for Sherlock's hand. Of course he was still Sherlock, what was he thinking? He was tired, that was all, the long nights with little sleep taking their toll. Would it be like this when the baby arrived, he wondered? Wandering around in a sleep-deprived fug, unknowing and uncaring what day it was, walking into furniture, so tired that he could barely string a sentence together? Would he even be living in the same house as his child when they were born? He pushed that thought firmly to the back of his head. Not now, he couldn't think about this now. This sleep-deprivation felt like the seventy-two hour on calls that he used to do as a surgical house officer, back in the bad old days, when nobody had even heard of the European Working Time Directive. No guaranteed sleep, and so tired that he had regularly lost the ability to talk at 3am, and on one occasion had stuck the syringe from the arterial blood gas syringe into his own finger instead of the patients wrist, and had failed to notice for several seconds, so numb from sleep-deprivation that he had felt no pain.

John's world had narrowed to Sherlock's room, the relative's room on the ITU, where the nurses had taken to feeding him sandwiches and cups of coffee while Sherlock was being washed or having procedures done, and the on-call room that James MacPherson had procured for him to sleep in when he could be persuaded to leave Sherlock's side.

He had tried to go back there to sleep, usually in the early hours of the morning, when the nurse stationed constantly in Sherlock's room caught him dozing in the chair, lulled by the symphony of sounds, and chased him out of the unit. But the sleep that had been so irresistible in the warm cocoon of the intensive care unit had proved strangely elusive in the barren on-call room. After what felt like several hours of lying there, willing sleep to come, he would fall into an uneasy dose, disturbed by dreams of Sherlock dying in front of his eyes, and being unable to reach him to help, separated by a partition of glass that refused to let him through, no matter how much he kicked or punched at it. He would watch the bullet enter Sherlock's chest again, and again, watch blood bloom on the white of his shirt, watch him fall backwards to the ground as if in slow motion, watch him gasp for breath as the pool of blood beneath him spread, and in all of them, John was entirely powerless, unable to reach him, unable to prevent the inevitable.

He rarely managed to sleep for more than a few hours before waking, heart racing, drenched in sweat, convinced that his dreams were a portent of what was to come. He would shower quickly, change his clothes, and return to the unit before the night shift had even begun to do their tally of inputs and outputs on the chart to prepare for the morning handover, and spend the remainder of the night dozing in the chair. He had an illogical fear of leaving Sherlock alone, as if by staying with him he could somehow give him the strength to ensure that he didn't give up. And underlying it all was always the knowledge that if something happened to Sherlock when he wasn't there, if he died alone, surrounded only by strangers, then John knew that he would never be able to forgive himself.

After three days of this vigil, John knew that he looked nearly as bad as he felt. Sherlock was hanging on but only barely. Transient improvements; an improvement in his blood pressure, a weaning down of the inotropes, would be followed as surely as night followed day by a deterioration in something else; a requirement for increased ventilator pressures or a drop in his platelets. John's days seemed filled with short-lived hope, followed by stabs of disappointment and despair. And through it all he sat there, holding Sherlock's hand, talking to him about something, anything; about the cases that they had solved together; about his ridiculous theories about what Sherlock had got up to in his time away; about exactly what he would do to all of his precious equipment in Baker Street if Sherlock didn't wake up and stop him giving it to the local high school to be destroyed by twelve year olds. But eventually, all of his conversations would disintegrate into him dropping his head onto the bed next to Sherlock, and whispering, 'Don't die, Sherlock, please don't die. Not again, I couldn't bear it. Come back to me.'

What he felt in those moments, he found hard to put into words. Love didn't begin to describe it as he watched Sherlock's sleeping face, the dark lashes curling on the pale cheeks, the exaggerated cupid's bow of his top lip, the slow rise and fall of his chest as it was inflated by the ventilator. What John felt for Sherlock in those dark hours before the dawn was like nothing he had ever experienced before; it was an utter immersion of himself in another person, a knowledge that somehow they were one entity, and that if Sherlock died, then what was left of John would be nothing more than a hollow shell. Mary was lost to him, not just because she had lied to him, nor because she was not the person that he had thought that he had married, but because she had knowingly tried to destroy the only thing in the world that John cared about more than her. And despite Sherlock's claims that it had been surgery, despite Mary's protests that she had miscalculated, John knew that he would never be able to forgive her for how close she had come to killing Sherlock, or the fact that she still might have succeeded in this.

If Sherlock died, then he would never be able to look at Mary again without remembering it.

If Sherlock survived, then he might never want to.

The guilt that he felt was overwhelming. Sherlock was lying there in a hospital bed, with tubes coming out of every orifice, hovering between life and death because of him. If John had never met Mary, then Sherlock would never have been shot. The facts were irrefutable.

And yet, and yet. Sherlock had risked his life for a second time to tell John that he could trust Mary. Why? Why was it so important to him? Try as he might, John could find no possible deduction that could explain the strange workings of Sherlock Holmes' mind. He would just have to hope that he could explain it himself when he woke up. If he woke up.

...

'No change?' Molly asked, walking into the room on the third day of the new antibiotic and antifungal regime.

'One step forward, one step back. His liver function is a bit worse, but his cardiac function is a bit better. Everything else is pretty much the same. And every day that he's like this, he gets a bit weaker,' John said, looking at Sherlock's sleeping face.

'He's a fighter. He's got through tougher scrapes than this before. He'll get through this one,' Molly said, determinedly.

'I wish I had your optimism, Molly,' John said.

'You look exhausted, John. Why don't you go and get some sleep? Or if you can't sleep then at least have a break, have a hot meal and a shower, maybe even get outside the hospital for a while. I'll stay with him while you're gone, and I promise I'll call you if anything changes.'

John shook his head, and started to protest, but Molly stopped him with a hand on his shoulder, 'You need to look after yourself too,' she said. 'When he wakes up then the real fun will start, and he will wake up, I know it. Look, I'm not working tomorrow. I can stay with him as long as I need to, all night if that's what it takes. Go and get some rest. Even if it's just for a few hours.'

John nodded, not trusting himself to speak, uncharacteristically moved by Molly's concern, and he surrendered his chair by the bed to her and headed towards the door for the unit.

He was halfway out of the door before he remembered that his phone battery was dead. The ITU staff lent him a spare bleep, its weight familiar in his pocket from his house officer days. He headed back to the on-call room, plugged his phone in to charge, had a shower and changed into some of his rapidly diminishing pile of clean clothes. He'd be into scrubs in a couple of days if he didn't go home to replenish his supplies. Knowing that he wouldn't be able to sleep, he instead went to the canteen to get some food, and then remembering Molly's advice, headed out of the main entrance of the hospital for a coffee shop round the corner, picking a stool in the window to sit and nurse his cappuccino, remembering with a smile Sherlock's derision of any form of coffee fancier than an americano. Double expresso had always been his poison, with as much sugar as he could dissolve it. Maximum caffeine and sugar hit with minimal time wasted on drinking it. Logical to the core, even when it came to beverages.

John picked up a newspaper that somebody had left on the table in front of him, only to be confronted by Magnussen's grinning face, and the news that he had acquired yet another tabloid. If John hated Mary at that moment, then he hated Magnussen a hundred times more. He almost wished that Mary had completed the job that she had gone to Magnussen's office to do; that she had killed the man. If she had done that, and not shot Sherlock, if he had discovered her secret after the event, what would he have done then? Could he have forgiven her for killing a man, for killing many men, for lying to him, if in doing so she had not come so close to killing Sherlock Holmes? The uncomfortable truth was that he suspected that he might well have done. For hadn't John done the same thing? John had killed more than one human being during his years in the Royal Army Medical Corps. All in self-defence, or the defence of his comrades. And once, just once, since his discharge from the army, he had killed a man to save the life of Sherlock Holmes, and he had never told Mary about that, either. She wasn't the only one with secrets. She wasn't the only assassin in the family.

And their child, what of him or her? What sort of life could this tiny bundle of cells have with parents like this?

John shook his head subconsciously, as if by doing so he could clear the thoughts from it. This was the problem with taking time out, with having time to think. Harder to push the messy tangle of impossible questions that his life had become to one side away from the protective bubble of the intensive care unit, away from Sherlock's side. All he knew at the moment was that he had to get Sherlock through this alive. He couldn't even begin to process how he felt about Mary and the baby and the layer upon layer of lies that she had told him until he knew that her bullet, and Sherlock's need to show him both her culpability and his forgiveness of it, had not cost Sherlock his life.

Pushing his cup of coffee to the side, he stood up, tucking the stool neatly back under the counter, the army training coming through as always. Then he picked up the newspaper and dropped it in the bin where it belonged as he headed back to the intensive care unit.

Explanatory Notes

1) Haemofiltration is a renal replacement therapy used on intensive care in patients with kidney failure. It involves putting in a 'Vascath' into a large vein, usually the femoral vein. This is basically a large tube with two lumens, one to take the blood away from the body and the other to return it back again. The blood then enters a machine which contains a filter, allowing waste products and water to diffuse out of the blood, and this is then returned with replacement fluid back to the patient.

It is basically a way of replacing the function of failing kidneys. In unwell intensive care patients, continuous haemofiltration tends to be used rather than traditional dialysis which usually occurs over a few hours, as it causes less of a drop in blood pressure, and is therefore better tolerated.

2) Magical thinking is a psychiatric / psychology term. Initial purest form it is the belief that thoughts or wishes can s affect external events, but it is also used to refer to the beliefs that seemingly unrelated events can influence outcomes, or have significance in a way that isn't possible, so for example, 'If the next car that comes round that corner is a red one then it means I should split up with my partner' etc.

It is a feature of some personality disorders, but is also seen in 'normal' people, at times of extreme stress. John would recognise it for what it was, but it is a way of trying to re-exert control in uncontrolled circumstances, so he'd probably just go with it.

3) Frusemide is a diuretic (i.e. it makes the patient pass more urine) used in heart failure, because the failure in the pump action of the heart makes patients retain fluid, hence fluid ends up in places that it shouldn't do, like the lungs (causing the pink sputum), the limbs and even the abdominal cavity.

4) Levosimendan is a very clever drug that helps the failing heart pump faster by sensitising calcium channels. Or something like that. J_Baillier would be able to explain it much better than me, but then she's a clever doctor.

5) Doctor Google - this is a very real thing! If you're stuck with a patient then you consult your colleagues Doctor Google or Doctor Wiki, often while trying really hard not to let the patient see what you are doing from the other side of the desk.

John is deliberately avoiding what he already knows - your chances of mortality goes up with each additional organ that fails. One study suggests its about 52% with three organ failure, going up to 88% with four organ failure. But then the mortality from fungal endocarditis is pretty high too. If I was John I wouldn't want to look at the statistics either.

6) PCR (Polymerase chain reaction) is a way of copying a short piece of DNA many billions of time, enabling the identification of viruses (or bacteria or DNA from crime scenes) from tiny pieces of genetic information. In this case, Molly is using it to identify the fungus that they presume is causing Sherlock's infection, but which is present in too small amounts to identify by traditional methods.

7) Citric acid - heroin is often cut with this to help it dissolve when heated. Finding citric acid under Sherlock's finger nails together with diamorphine (the pharmacological name for heroin) is therefore a strong indicator that he has been injecting it.