Mom and dad have sex with their stepdaughter

The scene opens with a young woman, a brunette girlfriend, sitting on the couch with her boyfriend. They are watching a movie when her father and his wife walk in. The father is clearly uncomfortable with the situation, but the woman's mother is eager to get to know her stepdaughter. She asks the girlfriend to show her some of her favorite moves, and the girlfriend eagerly complies. The mother is clearly impressed with her stepdaughter's skills and offers to show her some of her own moves. The father is clearly uncomfortable with this, but the mother insists. The mother and daughter start to dance together, and the father can't help but notice how close they are. He is clearly aroused by the sight of his stepdaughter dancing with his wife, and he starts to fantasize about having sex with them. The mother notices his arousal and invites him to join in.