The ridge I know by heart won't hold still

I'm guiding again on the route I could walk blind — the one I've done a hundred times. But the rock feels soft under my boots, like wet wood, and the silence between holds has a hum in it that wasn't there before. I keep checking my clients, and they keep smiling back like they can hear it too. That's when I realise we're not on the mountain at all; we're inside it, and the way out keeps changing.