You have been following me from almost the beginning.

Seed-black eyes, thread-fine whiskers, delicate claws that prickle and scrape. Darting and hiding, on your quest across the unswept concrete. I have found a rusted trap, and will welcome your company while I repair it, but you pay it no heed (does it puzzle you? amuse you?). Your course is set towards—not me, but my book.

That is how I know it is you.

Mortality was never my besetting weakness, but here are some creatures you have been:

A doe, milk-white, grazing near my cave one evening. Your hide would become the cover of this book.

A lamb, incautious, of whose skin I made the first parchment-page.

The pine (which fell before the doe was born) whose resin yielded soot for my ink.

Three lives, single-souled, to supply my pen. Although I have forgotten the language I wrote in, I can guess the meaning, for what does any man write, except I am here.

The coincidence that calls you back, life after life, to the book is also the power that makes its words true. The words shimmer and act, the letters ripple and be. But what do you want with it, little one?

I have beaten you and killed you, one plague year when you were a rat. Much, much later, when the secrets of disease were unlocked, I amused myself by imagining you became after that a flea, and after that, a fleck of the plague itself. In another half-emptied city, you were a thief, fumbling from hunger, only your soul carrying you forward. Justice was swift, there: I had you hanged.

There were times when you were long absent, although I suspect you were once a convolvulus spiralling towards my many-paned window.

You have certainly been a spider, in a city of sun-baked brick that is lost now to time. A little long-legged peace-lover, webbing and winding the book when you thought I did not notice. You were too small to even lift the cover, and so I let you linger, unthreatening company, as concerned with the book as I. When you died, curled in your strands, I almost mourned.

Twenty years later, when you were a handsome youth with gold on your upper arms and wrists, and royal scarlet daringly woven through your robes, they bore you on a litter to my door and you entered with wide, acquisitive eyes. I imagined that you remembered the taste of mites and moths, that your scarlet lips were still powdery with their wings.

You offered me much for the book, when you saw it—you recognised rarity and power, I think. You certainly knew bloodshed.

I can only conjecture, you see, what it will mean for you if you take my book, or for me if I lose it. I have written my long life in those pages (on skins I suspect you have worn, and on others no doubt innocent), since first I guessed its tripled power. It has sustained me when I have been pursued and threatened, when lesser men would have surrendered.

(Were you also the rabbit I boiled into glue? What of the flax that became the thread that stitched the pages? The reed that formed my pen?)

I have tried to make another such book, but there are more souls in the world now. How am I to find anyone twice, except you, who are bound to me? You, who remain undiminished, one of the first.

When you were a general, razing villages, and I fled with the book strapped beneath my clothes, I was curious: had you begun to remember the secret I whispered into the dying mouth of that arrogant lad? Or did you rage because you were crowded now by thin, diluted souls, you who had been almost solitary in the youth of the world?

Once, for a time, you recurred in the children of a new factory-town. Starved, or work-mutilated, or too richly dressed, always you found your way to my door, and always your eyes lit on that book. Each child—nine, or seven, or five—was of an age to have come into being on the death of the last whose body was buried under my floor.

Why that loop? Were children any cheaper, then, than they have ever been? Or had the pattern become familiar to you?

I, also, have a rare soul, and an old one. When the world grew over-full, I moved up among mountains, intending to watch them erode to their ancestral bones.

It took several lives for you to find me there, and I wondered if you were crossing the ocean to me on ships that plunged down to a darkness so undisturbed that it remembered you. Or were you ascending from the plains in a train that choked on its own smoke in a long tunnel, so that you died as peaceful as sleeping?

There was a young woman with a camera. Climbing high, she found my hut; it was seventy years before the retreating glacier released her body.

For some of that time you were an eagle, clear-eyed, but even when the great windstorms destroyed my shelter, I kept the book under a stone.

Would we ever have ended? If I had not written you into my life, would you have spread like dye through the clouded pool of history? Or if I had not bound my existence to yours, would I have died and lived as others do, diminishing, always seeking an immortality I surrendered in the first youth of the world?

(We loved each other, once, until you took the key I forbade you.)

If there are others like either of us, they are too knotted in their own stories, their own repeating secrets, for me to find them.

The Methuselah trees have fallen to storms or smoke, and the ancient sea-sponges are passing; there is a great lizard I have seen more than once, but perhaps it is merely old. Some sharks, I have heard, circulate in the currents for centuries—who knows what they have learned. And I am told the cockroaches will outlive everything else, take the lean, lost souls remaining into their number, and inherit the earth.

Even now, as I bait this trap with food from my own plate, I am certain of this: when the waters rise and the sun burns hot and close, I will ask myself whether I have seen the last of you. Yet what if we survive that, as well, and the world freezes like hate? Suppose, when you wade through ashen snow and find me, this book remains the only thing left to burn?

When ice brittles the water and the sky, and my breath is frost, you will come to me in your final body. You will curl at my foot, or alight at my elbow, or stand over me, and mean or even say, “This time, set us both free. Let us warm our hands a little at the pyre of all that has ever been, the lives I had and the lives you refused, and rest.”