In a moment of sibling rivalry, a brother and sister find themselves alone, bored, and horny. The young woman retreats to the bathroom, masturbating furiously with fingers plunging into her wet pussy. Caught in the act, they argue, but later, curiosity and lust draw them together. Naked and aroused, they masturbate openly, the brother's thick, straight cock hardening under her gaze. As they're about to cross the final taboo, an unexpected interruption forces them to abort their erotic encounter.