Ah. Yep, here we go. Sky pushes his prosthetic hand into a pocket. He'd strapped a watch to it and the watch has tiny glowing elements, enough to detract from the darkness. Their route was too convoluted for the sun to reach where they are now, so the only light is what they carry with them.

Normally, in the cave tours he's been on, he thinks about how bewildering it is when there's no difference between eyes closed and eyes open, when you want to touch your face just to check, and the phantom not-image of your own hand which your brain supplies. Now, instead, it's easier to perceive the people in the group. Sky listens to them. There are some insects here too, he's suddenly sure, wandering in from entrances and living on bat droppings and not a lot else.