In a cramped apartment, a sister and brother find themselves alone, their mutual attraction growing with each stolen glance. When he catches her masturbating in the bathroom, they argue heatedly, but their desires are too strong to resist. Naked, they explore each other's bodies, his thick cock throbbing as she strokes it. She fantasizes about him fucking her, and just as they're about to give in, a knock at the door forces them apart.