The fourth season of Masters of Sex began airing in the United States on September 11, 2016. The series is the television adaptation of Thomas Maier's biography Masters of Sex: The Life and Times of William Masters and Virginia Johnson, the Couple Who Taught America How to Love. It stars Michael Sheen as Dr. William Masters and Lizzy Caplan as Virginia Johnson.
The fourth season takes place in 1968 and 1969.
A month after their fallout, Bill's life is in shambles. After getting into a car accident, he is forced to go through AA meetings, where he meets Louise, who encourages him to keep going to the meetings even though he's not an alcoholic. Meanwhile, Virginia is in Las Vegas, after getting into an ugly breakup with Dan. She is anxious to capitalize on her fame, and wants Hugh Hefner to publish an article in his magazine. Hefner agrees, but will only invest in the business if Bill and Virginia continue to work together. Bill and Virginia agree to work together as long as the work stays strictly professional--and want to bring in new partners for the both of them.
Bill starts by hiring Nancy Leveau, a former associate of Barton's. Virginia retaliates by hiring Art Dreesen, a psychologist. Virginia soon finds out that Nancy and Art are married and in an open marriage. After a night at a swingers party lands Art and Virginia together, Virginia finally confronts her feelings towards Bill--and realizes she still loves him.
Meanwhile, Libby and Bill plan on having a divorce, after Bill revealed he has been having an affair at the end of the previous season. However, their relationship softens throughout the season. Because of their legal issues, Bill's lawyer, Bram Keller, tries to get Libby to not pursue the divorce until after the trial ends. Libby and Keller go on to develop a close, intimate relationship. Libby gets an offer to study law in California, where she moves at the end of the season.
Things get heated between Virginia and Nancy. Virginia wants Nancy and Art fired, especially as she learns Art told Nancy that he and Virginia had sex--which they did not. Bill allows the two of them to stay on. Nancy wants to start her own clinic with Art. However, after Art learns that Nancy aborted his child, he wants nothing to do with her and turns her in to Bill and Virginia.
Virginia continues to try and pursue Bill, who is reluctant to get back involved because he doesn't want to be hurt again. After going undercover to investigate a competing clinic in Kansas, Virginia reveals that she loves him, and he says he loves her too. The two, reunited at last, agree to get married. Even though Virginia's parents marriage is falling apart and Bill's family is moving away that day, Bill and Virginia finally get married, and are photographed by the press exiting city hall, husband and wife.
|"Freefall"||37||September 11, 2016|
|Bill, reeling after Virginia's departure, is forced to go to mandatory AA meetings after being caught drunk driving, and tries to turn his life around by returning to the clinic.|
|"Inventory"||38||September 18, 2016|
|Virginia learns that Bill has hired a new partner, as per their agreement, and begins looking for a partner of her own; Bill is intent on making things right with Libby.|
|"The Pleasure Protocol"||39||September 25, 2016|
|Bill and Virginia continue to work with their respective partners on several different new cases; Alice Logan returns; Libby starts a new job for a divorce lawyer.|
|"Coats or Keys"||40||October 2, 2016|
|Bill, Virginia, Libby, Betty, Lester, and Keller all end up at a swingers party hosted by Art and Nancy; Bill and Libby re-examine their complicated relationship.|
|"Outliers"||41||October 9, 2016|
|With their legal troubles coming to a resolution, Bill is forced to make a difficult admission; Virginia goes to New York to salvage their book deal.|
|"Family Only"||42||October 16, 2016|
|Virginia deals with insubordination in the clinic, and continues to try to reunite with Bill; Helen goes into labor and Betty is left dealing with an unforeseen tragedy.|
|"In To Me You See"||43||October 23, 2016|
|Bill contacts a lover from his past; Virginia and Nancy discover their clinic is under scrutiny from competing businesses.|
|"Topeka"||44||October 30, 2016|
|While investigating a competing clinic in Topeka, Virginia is horrified to learn that Bill and a former lover have met in person; Austin comes upon a new business venture.|
|"Night and Day"||45||November 6, 2016|
|Virginia is dismayed to hear that her parents marriage is on the rocks; Bill learns that Louise has fallen off the wagon; Libby and Bram get stuck in a traffic jam.|
|"The Eyes of God"||46||November 13, 2016|
|Bill and Virginia take precautions as they learn Nancy is planning on opening her own clinic; Libby plans on moving to California to study Law at Berkeley.|