The rain pours down, a relentless drumbeat on the roof, as the siblings huddle together for warmth. Their bodies press close, the thin fabric of their clothing doing little to hide the heat that radiates between them. They're slippery, their skin glistening with the rain that's seeped in through the open window. The room is dark, the only light the occasional flash of lightning, casting their shadows in stark relief on the wall. Their hands roam, tentatively at first, then with growing boldness, tracing the lines of each other's bodies, exploring the wet, slippery terrain.