A Thermal Perimeter

I descended from the bookcase ridge, moving along the carpeted floor toward the glass patio door. The noon sun had cast a sharp diagonal of heat across the threshold. I halted at the edge of the shadow, testing the floorboard with one foot. The temperature difference was noticeable. Instead of stepping into the brightness, I crouched low beside a dormant metal doorstop. I observed dust motes drifting across the beam of sunlight until the angle narrowed. A quiet shift in the room's perimeter.