The creaking floorboard reveals her presence, but the brother continues, lost in his pleasure. The sister, unable to resist, watches as he grips his cock, veins pulsing with need. She bites her lip, imagining the taste, the feel of him in her mouth. He picks up the pace, oblivious to her voyeurism, leaving her with a throbbing ache between her legs and a secret she can't wait to explore.