Sudoku

I've never understood your fascination with those number puzzles that seem to appear in every newspaper. You sit there for hours, staring at them, holding your pen like a surgeon's scalpel, eyes intently focused, lips moving fractionally. If I listen hard when it's quiet, I can hear rhythmic changes in your breathing, and I worked out that you're muttering to yourself just under your breath as you work out where the numbers go.

Every so often there'll be a sudden, darting movement as your pen lashes out at the paper and ink is applied with the precision of a tattoo artist working for the Yakuza. Your eyes will brighten for a moment, then tighten again and the rhythmic inflexions of your breath will pick up. There's a pattern there as well, you'll scribble rapidly at first, then slow down, and then finally there'll be a steady beat as the grid fills up and the choices for the numbers reduce.

But you never fill the last number in. Every grid you solve has a single, unfilled box. There's no question about the number that goes there, it's uniquely constrained, but you always leave it blank; you lay the puzzle aside, smile contentedly, and move on to something else.

I asked you once why you never finish the puzzle, and you gave me the strangest look. For a moment it was like your eyes turned inside out and something that should stay within you was all around me, something warm and huge and coloured with a hue I've only seen in nightmares. You told me that it was important that the numbers know their place.

I'm going to finish the puzzle for you. When you're done with one, when you lay aside the paper and put the pen down, I shall pick them both up and write the last number in, and see what happens.