In the dim light of the attic, the siblings huddle together, their bodies close but their minds elsewhere, haunted by the same forbidden desire. The brother's bladder is full, and the sister's eyes gleam with excitement as she watches him struggle to hold it in. "Do it," she whispers, her voice barely audible. He hesitates, but the pressure is too great. He lets go, his warm, golden stream soaking through her nightgown, drenching her panties, and making her gasp with a mix of shock and pleasure.