This guy suspects his girlfriend is hotwife on him, but he needs solid proof that she's a plumbing slut. That's why he has her tied and eyes covered and lets his friend drill her licking pussy to see her reaction when she discovers who's actually plumbing her. She makes it look like she's shocked and unwilling at first, but then her trampy side takes over and she loves sex with a total stranger as well as a messy cumshot like a real whore.