When Masters of Sex Season 4 Episode 4 begins, we see the aftermath of a party thrown the previous. Flash back to 24 hours earlier, Art and Nancy discuss inviting Virginia to their swingers party. At the office, Virginia and Bill discuss how to best handle a couple's therapy.
Virginia shows up to the party with Libby. Lester and Betty arrive together, and Bill planned on spending the evening with his children. After realizing his children are not home, Bill shows up at the party only to find Libby and Keller. Libby and Bill leave just as the night's events begin to change.
Virginia and the others are shocked to learn they are at a swingers party. It's men choice and they pick their choice of coat and that's the woman they will take home. Art grabs Virginia's coat, Lester runs out when a woman rejects him, and Betty grabs her own coat and finds solace with the gay piano player, named Guy.
While listening to his wife have sex in the next room, Art reveals to Virginia that he only swings to make his wife happy. Virginia begins to realize through Art that Bill is the only person to love who she truly is.
Back at Libby's house, Bill tries to apologize again for hurting her, but Libby wants payment. She tells Bill to go down her. Afterward, she reveals how she wished they had done things like that when they were married. They end up kissing and spending the night together.
When Virginia sees Libby's coat still at the house the following morning, she brings it to Libby's house. She's shocked to see Bill there. She finally reveals that she and Dan never married. Bill says he knows and says he'll see her at the office.
Betty and Guy bodn over the evening and both sleep over at the clinic.
Lester has a passion-filled night with a woman who was acting as a waiter at the party.