Forty feet in the air, with leafy branches tangling my workspace, I settled down on my haunches and pulled the pneumatic cable around, bringing my nail gun to bear. In a succession of sharp blasts, another mat of shingles was permanently attached to the plywood. The chalk lines I had snapped were fading, so I took care not to smudge them further as I moved along the sloped roof, back to where I kept the nails.

There came a shuffling of dry leaves. I knelt and racked a few more nail strips into my gun, snapping the mechanism shut again, scanning the ground below. The second level of this building had no roof or walls yet. Dappled sunlight streamed through swaying tree branches onto the workspace complete with sawhorses, scattered tools, power cables, ropes, and a compressor, all partly hidden under drifts of sawdust.

Dry rustling came again – from all sides, I noted – accompanied by guttural moans. Metal scraped against the walls. I stood and looked below at the dark shapes emerging from the ground.