In the dimly lit hallway, a curious sister spies her brother's bulge through his thin pajama pants. Drawn to his size, she tentatively reaches out, grasping his throbbing length. He gasps, surprised but aroused. She strokes him, feeling his cock grow harder in her hand. He turns, pressing her against the wall, his hips grinding into hers. Their eyes meet, and the unspoken understanding passes between them: they're going to cross a forbidden line.