I have a discovery to report. Many of the world's great treasures are known to have been lost over the centuries. I believe I may have found one of them. What follows is the evidence for my claim.

I'm in a difficult position, though. If my claim is not accepted by scholars I shall look a fool. If it is ... then I shall be in a worse position. The circumstances of the discovery are such that I shall emerge not only as a fool but as an object of outrage and horror.

I could say nothing, and no one would ever know. But if I have any pretensions to be a scholar — even to be a normally civilized human being — then I have an obligation to put my findings on record, so that my colleagues and successors, now and down the years, can evaluate them. And I must describe the tangled circumstances of this discovery of mine as fully and honestly as I can, because to arrive at a judgement they will need to examine them in the minutest detail.

Well, perhaps it's better to be known as a fool or a rogue than not to be known at all.

It's a painful prospect, though. Before I get to the end of this deposition I shall have to explain some shameful things. This anguish I feel about them is hard to endure. Even worse, though, is the anguish of my uncertainty about what exactly I have done.

Now, where do I start?

The obvious way would be to say what I think this treasure is. And at once a difficulty arises, because it doesn't have a name. I could simply describe it, and in due course I shall, but it wouldn't mean very much if I tried to now, because it's never been described before, and no one has ever had the slightest idea of what it looked like.

I think that the only way I can come at it, the only way I can bear to try, is to give up all attempt at a retrospective account. I shall have to go back in time to the very beginning, and relive what happened as it happened, from one moment to the next, explaining exactly what I thought as I thought it, when all the puzzles were actually in front of me, and what I was trying to do at each moment, given the possibilities that seemed open to me then, without the distortions of hindsight.

This has its disadvantages. My tone's going to sound inappropriately light minded at times. But that's the way it was. The tone of most of the things we do in life is probably going to turn out to have been painfully unsuitable in the light of what happens later.

So, from the beginning.

We're back in last year. Last year is now. It's early spring. A particularly appropriate jumping-off point, as will become apparent.

What's the first sign that something unusual's starting to happen?

I suppose it's a length of frayed twine.

The same length of twine, it occurs to me, that will bring the story to its end.