I'm up on the top of a very high pinnacle of rock, hundreds of feet above the ground. Four of us have climbed up there, including my sister Petra, and now we're playing some game with some black rocks that we found. "Watch this," I say, putting the rocks in what appear like old tree roots embedded in the rock, like I'm going to do some trick with them.

I notice that Petra isn't clipped in (for rock climbing, a safety connection to an anchor point that is used in such situations), and I say "Hey Petra, you wanna clip in?"

She stands up from where she was sitting with her pack, as though preparing to clip in, but she doesn't even seem to notice that the edge is right behind her, and without even looking, steps back and falls off. Our eyes meet as she falls, and she has a blank, desperate, hopeless looks as she realizes what she has done. I think for just a moment what to do, but there is nothing that can be done, as she plunges to her death.

"Don't look," I tell the others. "Really, don't look."