In the post-apocalyptic wasteland, Catherine, a young woman living in a Vault, finds solace in her brother's company. One night, as they huddle together for warmth, Catherine's thoughts turn lustful, eyeing her brother's rugged, muscular form. She begins to touch herself, her breathing growing heavier, her pussy growing wetter. Her brother, awakened by her movements, watches her in the dim glow of the Vault's emergency lights, his cock hardening in his pants. Catherine, emboldened, invites him to join her, their taboo desires consuming them as they give in to their nuclear family's forbidden passion.