Much human ingenuity has gone into finding the ultimate Before.

The current state of knowledge can be summarized thus:

In the beginning, there was nothing, which exploded.

Other theories about the ultimate start involve gods creating the universe out of the ribs, entrails, and testicles of their father

But this story starts on the Discworld, which travels through space on the back of four giant elephants which stand on the shell of an enormous turtle and is not made of any bits of anyone's bodies.

But when to begin?

Thousands of years ago? When a great hot cascade of stones came screaming out of the sky, gouged a hole out of Copperhead Mountain, and flattened the forest for ten miles around?

The dwarfs dug them up, because they were made of a kind of iron, and dwarfs, contrary to general opinion, love iron more than gold. It's just that although there's more iron than gold it's harder to sing songs about. Dwarfs love iron.

And that's what the stones contained. The love of iron. A love so strong that it drew all iron things to itself. The three dwarfs who found the first of the rocks only got free by struggling out of their chain-mail trousers.

Many worlds are iron, at the core. But the Discworld is as coreless as a pancake.

On the Disc, if you enchant a needle it will point to the Hub, where the magical field is strongest. It's simple.

Elsewhere, on worlds designed with less imagination, the needle turns because of the love of iron.

At the time, the dwarfs and the humans had a very pressing need for the love of iron.

And now, spool time forward for thousands of years to a point fifty years or more before the ever-moving now, to a hillside and a young woman, running. Not running away from something, exactly, or precisely running toward anything, but running just fast enough to keep ahead of a young man although, of course, not so far ahead that he'll give up. Out from the trees and into the rushy valley where, on a slight rise in the ground, are the stones.