I should tell you about the oldest world, because it is where the thing I carried came from, the one thing my world had that the other two needed.
The oldest world is the one most people go to live in when they leave their own. It was built so long ago that nobody remembers by whom, and it is so large that you can be born in one part of it and die in the same part and never have seen a far wall. Everyone who lives in it works on it: roads always being mended somewhere, roofs always being raised, ledgers always being added up in a room you have never been to by people you will never meet. And because the work is the world's and not yours, the days inside it are short. A year there is a handful of afternoons.
When I was a child, my family lived in the oldest world, as most families do, and I was given a job, as children are, and the job was finding. Things go missing in a world that size the way water goes missing in sand. A ledger, a lamp, a wedding ring, a whole room, once, with the people still in it. The finders are children because children are small and cheap and do not yet know that a thing can be truly gone. I was good at it, because of how I listen. A lost ring thinks about the finger. A lost ledger thinks about its numbers, faintly, like someone counting under their breath in the next room. I would walk the corridors with my head on one side, and after an hour or a day I would hear it, and there it would be.
Then, the year I turned eleven, they sent me for the far wall.
The far wall of the oldest world is a thing people speak of the way they speak of the sea. Everyone agrees it must exist. No one you know has seen it. A ledger-keeper had decided that the world could not be properly accounted for until someone had touched its far wall and come back to say so, and the finders were sent, one after another, and came back, one after another, having found nothing but more world.
I was gone a year. I will not tell you all of it. I will tell you that I slept in rooms no one had entered in a generation, where the dust lay so thick and even that it had become a kind of floor. I will tell you that I found the room that had gone missing with its people in it, and that they were fine, and had built a small life, and asked me not to tell the ledger-keeper, and I never did. I will tell you that I listened for the wall the whole year and never heard it, because a wall does not think about being found. It thinks about the wind on the other side of it, and I did not know that yet.
And I will tell you that in the end I found it by accident. I was going down a stair I had been down before, and I put my hand out to steady myself, and the stone under my hand was cold in a way no stone inside that world was cold, and I stood very still and heard it, very faintly, thinking about the wind. I had been past that stair four times.
I put my palm flat on the far wall of the oldest world. It took about as long as it takes to say it. Then I turned around and went back, and the going back was three weeks, and I told the ledger-keeper, and she wrote it down, and that was the end of it as far as the world was concerned.
But it was not the end of it for me, because of one thing. When I had told her, she asked me to draw the way. I did my best. It was hopeless. The way was a year of corridors that led to corridors, and the one stair with the cold stone was the last inch of it. She looked at my drawing and said, gently, that it would not do, and folded it, and the next finder they sent was a boy of nine, who went off down the same corridors from the beginning, as if I had never been.
I lay awake that night and I thought: I took a year, and the touching took a breath. The finding is slow and the knowing is fast, and the gap between them is where the year went. And I thought: someone had touched that wall before me. Someone must have; the world was built from that wall outward. And whoever it was left, and took the way with them, and every finder since has had to begin again from the first corridor.
That thought did not leave. It sat with me through seven short years, and I turned it over so many times it went smooth. What if the finding only had to happen once. What if the way, once someone had walked it, stayed. Not the walker; not their name, not their reasons, not their year. Only the way. Then what was nearly impossible for the first would be a morning's walk for the second, and the hundredth would be born at the cold stair and never know there had been a world to cross.
And our own worlds were the same problem wearing a different coat. Every person born with one. Almost no one who builds theirs. Because whoever did build one, back at the beginning, left the world and took the way with them, and every child since has been handed a doorway and some open ground and no idea what comes next.
I did not have the answer. I had the shape of it, and the cold of a stone under my hand that I had never forgotten, and the certainty, which I could not have defended, that the way could be made to stay. I could hear it. I could not draw it. That was what I carried, and I could not set it down anywhere in my own world, because my world had no floor to set it on.