In the quiet of their shared home, a brother and sister, primos, find themselves alone and horny. The brother, watching from his bedroom, catches his prima masturbating in hers, her moans barely muffled through the thin walls. He can't help but stroke his cock to the sight of her, her fingers working her pussy. She soon notices him, and instead of stopping, she invites him to join her. They masturbate together, eyes locked, until they both reach climax.