The vault’s lights ran on motion sensors, and I learned this in the worst possible way: every time I went still, the room dropped into total blackness, and every time I moved, it flickered back.

The message of that was simple and horrible.

If I stopped moving, the dark came.

And in that cold, if I stopped moving long enough to sit, I would grow warm and drowsy in the way that the freezing do, and I would sleep, and my children and I would never wake.

So I did not sit down.

That was the whole of my strategy, and I clung to it like a rope over a cliff: I would not sit down.

I walked.