One leaf.

Come! He owed it to his friend.

Just one leaf.
Were there English butterflies here as well?
Yes.

Here was a sheet of them.
He knew that little yellow one with red tips to its wings.

It was common enough in the south of England.
He looked idly at it.
And somewhere out of the past, far, far back from behind the crystal screen of childhood, came a memory clear as a raindrop.
He remembered as a tiny child lying in the sun watching a butterfly like that; watching it walk up and down on a twig of whortleberry, opening and shutting its new-born wings.