A bored, horny sister sneaks into the bathroom, her masturbation session cut short by her brother's sudden entrance. Caught red-handed, she lashes out, their argument escalating until they're both panting and flushed. Later, they find themselves drawn together again, this time naked and explicit. The brother's massive cock stands at attention, and the sister can't help but fantasize about it filling her. Just as they're about to cross the final line, a third party enters, forcing them to abort their erotic encounter.