In a cramped room, a brother and sister, both teenagers, find themselves alone and aroused. He starts to touch himself, his cock hardening in his hand. She watches, biting her lip, as he strokes faster, his breath hitching. She can't resist the urge to join him, her hand slipping into her panties, finding her clit. They lock eyes, their siblings' bond morphing into something more carnal as they masturbate openly in front of each other, their bodies tensing with impending orgasms.