In the dim light, the brother's hand trembles as he tentatively reaches for his sister's intimate folds. Her gasp guides him, his fingers tracing her slick labia before plunging inside. He curls them, finding that sweet spot, as she grinds against his hand, her hips bucking. Their hearts race, their bodies tense, but a sudden noise forces them apart, leaving them both craving the unfinished dance of their fingers.