As the thunder rumbles outside, so does the siblings' pent-up passion. Their bodies press together, soaking through each other's clothes. She grinds against his thigh, feeling his hardness, while he slips a hand under her gown, finding her wet, ready slit. They kiss, tongues tangling, as they rut against each other, their movements frantic, desperate. The room fills with the scent of sex, the sound of wet, slapping flesh, and their ragged breaths as they teeter on the edge of ecstasy.