Masters and Johnson adjust to new partners, but their respective cases have them second-guessing the instinct to remain separated. A romantic prospect pushes Libby to embrace life as a newly single woman of the sexual revolution.

Johnson, Masters, Libby and Keller wind up together at a party thrown by Art and Nancy. Pairings and perspectives shift as the night wears on, until the light of day exposes the consequences of the evening.

Johnson and Masters' troubles come to a head as the trial begins with Keller leading the charge. Virginia does her best to revive their career as Bill faces the reality of what the charges could mean for him, Johnson and the practice.

Johnson looks to get her relationship with Masters back on track while Masters does his best to find satisfaction elsewhere. Betty and Helen ready themselves for a new addition; Art and Nancy discuss the consequences of their party.

Masters and Johnson go on the road and pose as a couple to investigate practices at a competing clinic. While Bill and Virginia are away, Art, Nancy and Langham take advantage of their absence to further their own agendas.

Masters and Johnson return from Topeka, each grappling with the trip's ramifications. Art and Nancy look to tie up loose ends in order to have a fresh start, and Libby embarks on a road trip with Bram that changes her perspective.

Masters and Johnson work to save the practice from disintegrating in the face of insurrection within the clinic. As everyone in their lives either moves on or falls away, Bill and Virginia find solace in one another. Season finale.