Maupertuis indicated us with a flick of his head.

'Surd,' he whispered to the man behind him, 'kill them.'

We leaped back into the room and I slammed the door. There was a cheap bolt on the inside: I threw it, but it wouldn't stop Surd for long. Holmes tried to open the door again, crying, 'I must see the other man!', but I pulled him towards the window.

'The drainpipe!' I gasped. He picked up my meaning straight away, and clambered over the window-sill. I gave him a few seconds to get clear, then followed.

I still have nightmares about that climb. More than once I felt the bolts that attached the drainpipe to the wall start to give. Rust scoured my hands, and a b.l.o.o.d.y haze seemed to hover before my eyes as I called upon all my reserves of strength. I paused to look up at one point, and saw Maupertuis and the cowled figure of his companion leaning out of the window watching us. Of the menacing Surd there was no sign. I presumed that he was racing down the stairs to catch us. In my panic my foot slipped, and I was left hanging by a supporting bracket whilst my muscles screamed for release.

My flailing feet found a brick which projected slightly from the wall and I resumed my climb, drenched in sweat. I could not tell how far I had come, or how much was left. My universe was a stretch of crumbling brick and a cast-iron pipe.

'Jump!' Holmes's voice shouted from below. Trusting him, I let go.

It felt as if I was hanging unsupported in mid-air for an eternity, but the drop could have been no more than a few feet. Holmes steadied me, then pulled me away across the garden towards the wall.

'Oy!' a voice yelled from the direction of the house. I ignored it, and pounded after Holmes. A hand caught my jacket, and I was pulled up short.

Turning, I found myself in the grip of the greasy-haired footman.

'What's your game, then?' he panted. I planted a short jab to his solar plexus and a cross-cut to his jaw. He'd been in a sc.r.a.p before, though, and shrugged the blows off without letting go.

Over his shoulder I saw Surd leave the house and lumber towards us.

Holmes had reached the wall by now, and was urging me on. I redoubled my efforts.

Surd paused, stood upright, and gazed strangely at me. A warm breeze stirred my hair. It must have been a reflection of the sun, but it looked to me as if his eyes were glowing.

I tried to jerk myself out of the footman's grasp, and succeeded too well.

Staggering backwards, I caught my foot in a clump of weeds. I sat down, hard.

It was that which saved my life.

As the footman grinned down at me I felt, rather than heard, a sudden whumph, and watched in disbelief as his head was engulfed in flames. He screamed and flailed his arms around. I scrabbled backwards through the garden on my hands and heels. He was jerking like a marionette in the hands of a drunkard. The flames were spreading down his shoulders and arms. As I watched, a fiery seam opened up across his chest. I was screaming too, as Holmes hauled me up over the wall and pulled me along the road, out of sight of the burning man, but not out of range of his agonized shrieks.

Chapter 7.

In which Watson and the Doctor attend a family reunion where much is explained and an unusual guest is introduced. explained and an unusual guest is introduced.

Holmes dragged me around the corner and onto the street. My side was raw with the pain of running, and the old Jezail bullet wound in my leg throbbed with a hot, insistent beat. I kept gulping for air, but it seemed that no matter how fast I panted, it was not enough. My stomach was in revolt, and I paused for long enough to bring up a thin, acrid bile before Holmes pulled me on.

Eventually he slowed and allowed me to collapse against a lamp-post. He glanced back urgently. I tried to follow his gaze. Although my eyes were watering, I could see that the street behind us was empty. Everything seemed normal. The birds were singing, the sun shone upon scrubbed steps and a cat padded along a wall.

And yet, not five minutes walk from where we stood, a man was burning like a Roman candle.

'They do not seem to be pursuing us,' he said finally. Apart from a slight flush, he was unaffected by our escape. 'No doubt they are worried about attracting attention.'

'Holmes, who are they?'

He frowned.

'These are deep waters, Watson,' he said finally. 'I confess myself adrift.

What we have seen today is not amenable to deductive logic, and yet...'

'And yet it happened.'

My breathing was coming under control now. My stamina had never fully recovered from my wounding near Maiwand and a subsequent bout of typhoid in Peshawar. It never usually let me down when I made demands: it just extracted its price later. I would probably be laid up for a couple of days after this.

'I need to think,' he said distractedly.

'Perhaps Mycroft...' I ventured.

'No. No, not Mycroft . . : Holmes glanced briefly at me, debating whether to let me in on something. I was well aware that there was some player in this mystery whose ident.i.ty was being kept from me. 'But perhaps...'

The clatter of a four-wheeler made us both jump. It was coming from the opposite direction to Drummond Crescent, and I relaxed as Holmes hailed it with a short blast upon his whistle. It slowed to a halt as I pulled myself to my feet.

'Baker Street,' Holmes barked to the m.u.f.fled cabbie, 'and double the fare if you make good time!'

He opened the door and aided me into the shadowed interior. I sank gratefully into the upholstery.

'Thank Heaven for small mercies,' Holmes muttered with heartfelt relief as the growler clattered off.

'Let's not get personal,' said a voice from the shadows. 'Small but perfectly formed, I think you'll find.'

A figure leaned forward into the light from the windows. I groped for my revolver, then remembered leaving it back at Baker Street. The four-wheeler turned a corner, and a shaft of sunlight suddenly illuminated our fellow-traveller's features.

'Doctor,' Holmes snapped, 'is that you?'

'Let's pretend it's not,' said the Doctor, 'and see what happens.'

'I presume that this is no accident.'

'Given the random nature of quantum interactions,' the Doctor mused as the cab turned again, and I saw the great hall of Euston Station through the window, 'can the confluence of any two events be truly described as anything but accidental?'

'I refuse to bandy words with you, Doctor. Give me a straight answer.'

'I prefer bandy legs to bandy words,' the Doctor murmured. 'An answer to what, Mr Holmes?'

'To my question.'

'You didn't ask any question.'

'I quite patently did.'

'Oh no you didn't!' the Doctor chanted, grinning.

'Oh yes I . . : Holmes pulled himself together with an effort. 'I distinctly asked you what you were doing here.'

The Doctor gazed owlishly over the curved handle of his umbrella.

'No,' he said, 'you merely presumed that my presence here was no accident.'

'The question was implicit!' Holmes almost spat the words out.

'What question was implicit?'

'What are you doing in this cab?'

The cab swerved slightly as a growler overtook us at some speed. Our cabbie cursed the driver in earnest and graphic terms.

'I'm following someone. Or perhaps I should say something.'

'Pray explain yourself, Doctor.'

'Oh, I'm not sure I could do that.'

He smiled.

'However, perhaps Doctor Watson here has told you that he has been followed ever since we left Mrs Prendersly's house.'

Holmes shot a disappointed look at me.

'I have not been followed!' I protested. 'Holmes, you have taught me enough about detective work that I would be able to tell if any man were d.o.g.g.i.ng my footsteps.'

Holmes smiled slightly.

'I myself have followed you during a number of our cases,' he said, 'in situations where I have antic.i.p.ated some attack being made upon your person.'

'But I have seen nothing,' I exclaimed.

'That is what you may expect to see when I am following you,' he replied smugly.

'What makes you think that it is a man?' the Doctor interrupted.

'Because should any lady within a three mile radius show the slightest interest in Watson,' Holmes said, smirking, 'then he would know about it.'

The Doctor drew back the curtain of the trotting cab and indicated an alleyway ahead with his umbrella.

'Do you see?'

I peered towards the alley. It was mostly in shadow. I could make out no human form within it, just a pile of sticks set to form a rough stand, reminiscent in form of the iron 'cat' set in front of the fire at Baker Street upon which Holmes and I were wont to toast m.u.f.fins on winter evenings. I had seen its like elsewhere, recently, but where?'

It vanished.

'Great Scott!' I exclaimed.

The Doctor pointed ahead to where a tree stood by a corner. A bundle of twigs was leaning up against it.

'A fast mover,' the Doctor said. 'Faster than the human eye can follow, at any rate. That probably indicates a race who are preyed upon by hunters of some sort.'

I tried to focus upon the . . . the animal, if the Doctor was to be believed . . .

but it moved again.

'I've seen similar behaviour in Raston Robots,' the Doctor murmured, 'but never before in a living creature. The energy it requires is phenomenal.'

He leaned out of the window.

'Around the corner!' he yelled.

'Right, guv,' came the resigned voice of the cabbie.

The growler veered sharply to the left, and Holmes peered out of the window.

'I see nothing,' he said.

The Doctor pointed to a pile of refuse, beside which I again saw the twigs.

'But what is it?' I cried.

'I don't know. I pursued it here from the Diogenes Club. I think it had followed you there, and lost you.'

'You cannot possibly be serious.'

He gazed at me with eyes that seemed to contain the weight of the world within them.

'Can't I?'

I leaned back in my seat and tried to make sense of what I was being told.

Try as I might, I could not fit this particular piece into the rational world-view which I held. It came from a different puzzle entirely.

The cab trotted on whilst I wrestled with my thoughts. The Doctor kept on yelling instructions out of the window, and Holmes tried and failed to see what we were following. Eventually we began to slow down, and I roused myself from my thoughts.

'Where are we?' I asked.

'Holborn,' Holmes and the Doctor said as one. I joined in as the growler halted: 'And the Library of St John the Beheaded.'

Of course. Where else?

Holmes stepped out into the street. I joined him. We were in more or less the same location in which Holmes and I had been dropped the day before.