Three's a Crowd is the second episode of Season 3 of Masters of Sex.
Bill and Libby try to legitimatize Virginia's sudden pregnancy by putting George back into the equation; Bill and Virginia take on a new patient while Bill takes on a new co-worker.
Virginia confirms to Bill that she is pregnant. She also reveals that the baby is George's, and that the two shared a moment from the lake months earlier. Virginia says that she has scheduled an appointment to have an abortion.
Weeks later, Bill and Virginia are expected to see the visit of the Shah of Iran and his wife. The Queen is having trouble getting pregnant. The Queen notices that Virginia is pregnant and congratulates her. The Queen, however, ultimately is unable to have children, and the Shah divorces her.
Bill, learning that Virginia is still pregnant, asks Virginia to take a leave of absence until the baby is born, and says that he has hired a clinician, Christine Wesh, to replace her until she returns.
Virginia is confronted by Libby, who is upset that people will believe that the baby is Bill's. After Bill and Dr. Wesh have no chemistry together in the exam room whatsoever, Bill realizes he needs Virginia back, and asks George to participate in a sham marriage with her to make the birth of the baby legitimate. She and George get married at the Masters' home.
Virginia goes into labor, and Bill comforts her as she panics in the hospital room, claiming she is not a good mother because she isn't ever around for her children. Bill tells her that she is a good mother because she's out of the house, because she isn't stuck indoors, and can bring things back to her children no other mother could. The baby is born, and Bill goes to a nearby bookstore to see Human Sexual Response--he and Virginia's baby--in the store window.
The previous episode ended in October 1965, and Human Sexual Response was released in May 1966, so the episode should take place between those two dates.