Alone in the house, the curious sister decides to put on a show for her brother. She slips into a tight, sheer nightie, straddling a chair in front of the open window. She starts by running her hands over her body, cupping her breasts, then slides a hand between her legs, rubbing her pussy through the thin fabric. Her brother, outside, sees her and can't help but watch as she slips a finger inside herself, biting her lip in pleasure.