Two days is a long time to wait around. With no more evidence than we already had there's less and less hope by the minute, more and more like all we can do is wait for the mistake. Which shouldn't be an option. A simple matter of patience, fine. Some choice granted in the killer's communications, difficult, but it could be dealt with. But this act of just waiting… Pretending to work, to look for solutions, just so nobody has to look responsible for the fact that there is no choice but to let a murderous sociopath do his bloody thing, and even then there are no guarantees. Two days is a long time to live with this.

I had thought the sheets might have been a saving grace. The traces, that the killer lay on them. Thought that might help.

But Lestrade was able to call me from his office line yesterday. Just briefly, just to let me know, that because the hotel guests had slept there before they were murdered, and because none of the household sheets on Friday Hill had been changed very recently, there was, and I quote, 'no time-efficient way to isolate a single genetic print from hair or fibre, and they won't test for sweat.'

I said, "Sorry, that's 'won't'. As in the contraction of will and not?"

"Yeah."

"Not 'can't', that wasn't what you meant."

"No. They can never make it stand up in court, so they're not going to take that chance."

"So they'll just take the chance on not catching him. Right. Sensible. No. Explain that to me again?"

He couldn't. And then he asked if I wanted to meet him for a drink. Subtitles were saying the nasty men at work weren't letting him join in anymore. My instinctive reaction was 'no', phrased differently, calling on God and with more expletives. Out loud, I made excuses about my current attempts at sobriety, the temptations of the hospital. The ones I didn't have to bring home with me and wish I hadn't.

But then the call was over and the two day wait resumed. Two days, and I had to lock the bedroom door on myself again. Nothing to do with sickness or even any real physical craving. Just the temptation, just what was under the kitchen sink, and just not being able to throw it out.

Sleep, maybe you can imagine, was difficult. It usually is, when you're waiting, and it is when you're sore, and it is when you want something and you're trying not to want it. I've been aware of myself most of the night, so close to consciousness that even when the clock does skip ahead thirty or forty minutes at once, it feels like I've done no more than blink. Not only that, but it becomes increasingly more difficult to move, even to think, and everything slips away in a haze, with me lying still as a stone at the centre of it.

It's the fastest I've been able to make the seconds move since before the hospital. Hellish, yes, but like so many other things it does the job. The pain is no more nor less and moves quicker.

After hours of this, I am sailing wonderfully close to the dark again, when the phone rings.

You could have timed that. If you'd been watching me and been so inclined, you could have counted the bloody thing in. So I'm not surprised, and I'm not annoyed, and all I do is roll out my hand to the bedside and bring it to me.

"Yes?"

"Sherlock?"

Donovan. Sounding tense, lowering her voice. Forgive me for thinking the word 'promising'. "Definitely the person you called."

"I… I'm not sure what's going on. Hazell's here so I can't talk to Lestrade, but I think he wants you brought in."

"But Hazell's there so-"

"But so are the news-crews, just arriving, so we've got another ten minutes of his company maybe before he goes to grimace at them."

"News-crews. You're not at Scotland Yard?"

"No." She doesn't explain any more than that. We both know that that means.

"How many?"

"Seven." Bringing the total to twenty-one. It shouldn't be possible. That scale should not apply to this sort of crime. And we were waiting for it, and only on the off-chance he's made a mess of it. I was waiting. I was lying in bed and I was waiting for it. Three strikes in as many weeks, slightly less even and twenty-one… Seven last night… Donovan interrupts this base, circular thinking. "Can I give you an address?"

"Yes. Of course."

That's exactly what she gives me. Street name and building number. An address. Not a word about what sort of a place it is. That's unusual. Her culture, the way she speaks, everything I know about her, that sort of precise detail doesn't match it. She would be casual. She would leave me dependant on the knowledge and kindliness of cab drivers to get me there.

She could have just told me it was one of the halls of residence for Goldsmith's. 'Batavia' would have been a helpful addition. That's what I find out when I get there.

I have the cab let me out at the corner. Down the street, Hazell is suitably distracted, and has an audience of lenses and microphones paying attention to him. Still, bit rude to just walk in the front door behind him. So I go round the back. Start making note of the back office, where there would have been a guard, I'm presuming overnight, and where was he when all this happened, who was patrolling. Close-quarters living. Someone must have seen or heard, but if so then why wasn't I called until after ten in the morning, and…

And then it all stops. Because at the back of the building where I am are the gathered students and staff all waiting to be asked these questioned, the shaking and smoking and crying, being protected so far from the cameras but that won't last long. And away from them, protected from them, is a boy not all that much younger than me, wrapped in an orange blanket, and his father is hugging him.

Before I know it, Sally Donovan is at my shoulder, looking past me at the same thing. At Lestrade, and… "His name's David."

Well, yes. Growing up with a French surname, you have to give the boy a Dave or a Jim or a Harry to lean on, don't you?

"Sherlock?" she's saying. I know she's saying. I just can't answer her. There's a man over there holding his pale, shaking son. No more or less than this. Donovan is saying my name and it's as much as I can do to turn away and reach for a cigarette.

Mycroft. Fucking. Holmes.

Two days. Two days and all I have on him is a very polished, very corporate-portrait type picture which tells me nothing and records from eight different government departments with his name on them which don't actually record anything. Seriously. The name is like a virus. It appears and everything else just vanishes around it. MOD, SIS, Home Office, all of it. The name and nothing else.

I'm not ashamed to say that I depend on records. This one little bit of stumping, this one little block, is not making me ashamed of that, because it's the only time I've ever come across it. There are always records. Even if you have never been to the doctor's, you were born, and I have your birth certificate. You've never taken out a credit card, I will get your mobile phone bill. You exist, you live, therefore there is record but there is no record. If Dani and Moran couldn't assure me that they'd seen the man in person, I'd think he was some sort of elaborate construct; a scapegoat maybe, a way for the government to fob things off. The buck stops with a man who isn't real.

Mycroft Holmes is Roger O Thornhill. I would have come to that conclusion, thought I was very smart, and walked away from all of this. But I know he exists. I know he exists. I know it. He is there to get and he will be got.

Nobody's rushing me, y'know. I've never had such patient clients in all my life. Never had two onto the same target before and they're ideal. They don't pester, they don't wonder if I got their call… Nothing. Moran hasn't mentioned it once. He keeps an eye, but he'll wait. He's happy to wait. He'll look at me and know when I've got something. Dani's mentioned it a couple of times, but not in a pushy way. Making conversation. She's starting to stink of her cigarettes, but that's the only outward sign.

No, nobody's rushing me on this. Maybe that's why I can think of nothing else. Can do nothing else. Can work on nothing else. The Creep hit where I told him to hit, and did it with skill and panache and I don't even care because this man exists and I cannot lay hands on him and it is not normal. The only difference is that, for once, nobody keeps trying to tell me to take a break.

So I'm working at it again this morning, and coming towards eleven o'clock, as ever, I hear the door open and close. Still haven't sorted out about any kind of signal. To indicate my presence and solicit whoever is in the hall's, "Hello?"

"S'only me." Danielle. Sounds tired, and relaxed. Good signs, both. She takes her time too. Hangs up her jacket and comes in wafting a mens deodorant. So things, I know, are going well with the married man. No honest, thoughtful mistress wears perfume. Don't ask how me and her ended up having that conversation, but it was unexpectedly interesting.

Anyway, she comes along, and I hear her in flat shoes (so she was indeed out last night), yawning just outside the room. Thinking, c'mon, y'bitch, ask why there's no coffee. I'll be wonderful, really good fun, when she asks me that question. I'm going to slit her up the middle and stretch her out to either side so everything inside gleams when she asks me that fucking question.

Of course the cow comes in with two Starbucks cups in a cardboard holder and denies me that.

She sees what I'm working on when she brings it to me. "Still no luck?" she says. There is just a trace of worry. We're at the stage where, any other task, any other job, she'd pull out the plug of the computer and escort me with tortures of contact, with the hairs out of her hairbrush, to somewhere where I'm supposed to relax. The usual definition is somewhere where I can't work.

I say, "No."

She says, "Not to worry. You'll get there. You always do." Sounds so sure of that, too. Moran said something similar at the start of this. They have so much faith. They think I'm so trustworthy, when it comes to this business. They're not rushing me, they're just so… sure.

I swear I'm not changing the subject, "I take it luck hasn't been a problem for you, then?"

She settles on the couch across the office. "I hate roulette. It's so random. I kept beating him. It was not good for what I'm trying to build. But it's his game, so what could I do?"

"That's that unicorn of yours kicking in."

"They didn't know the Creep was working as we spoke, so I'm not entirely up to date. They were stumped, at last report. As good as admitted Carl's holding all the cards."

"Good."

"Thought that would please you." She sits there a while. After that, cuts her eyes over, "Thought it would please you a bit more than that, if I'm honest."

"Really, I'm very happy we've found yet more proof that cops are thick, but Christ the Lord, Danielle, this silky-haired fucker's the invisible man. Actually, no, he's worse, because the invisible man was a scientist before he was invisible, and there would be records about him, and his education, and his training, and where he worked and… Where is all that? Where am I not looking?"

"You haven't missed it. It's there. We'll get there."

Yeah. We. Plural. Including her. "What about you? Where's your poor sad boy with the connection to him? You only told me you could have killed him."

She shrugs, tosses her hair. "Never looked into it." Says that like there's no more to it and she doesn't expect to be questioned any further on this topic. Well, that might work on pathetic men with too much job pressure and understanding wives, I can see how it might. But me, I just think that's an interesting reaction.

"Where's your poor sad boy, Dani? Asked you a question."

"I answered it," she breezes. "Not a Foggy Nelson, Jim. He's just a runner, anyway, he's not an option."

"He knows him. He's seen him, in all his glorious existence. He is a contact, and you are denying me-"

"That's why I'm not complaining about you taking forever to find one man we could have had killed this time last year when at least the fucking sun was out, so kindly do not push me to say anything less charitable than I absolutely must."

"He tried to use you," I tell her. And tell her, actually tell, in case she hasn't noticed, because it baffles me. "Whoever he is, whatever reason he had for doing it, he was going to use you to get to me."

Another shrug. "He's not an option. All you need to know. We can argue about this, but you will get nowhere and we will not find the one-man-government department and-"

"Say that again…"