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.

Masters and Johnson continue their sexual response study – now as participants – but Johnson fears their work may be interfering with Masters’ home life. Libby pressures Dr. Haas to resume her fertility treatments in secret. Meanwhile, Haas struggles to let go of feelings for Virginia as his relationship with Vivian deepens. And Margaret Scully, caught in her infidelity, confronts her husband on the mounting problems in their marriage.

When Masters and Johnson decide to film external reactions in the study, they must convince Lester and Jane that their footage won’t cross the line into pornography. Haas and Vivian’s plans for a Presbyterian church wedding are sidetracked when Haas reveals he’s Jewish. Libby keeps her pregnancy a secret from Masters and instead encourages him to mend his relationship with his mother. But during late night visits to the hospital, Estabrooks observes Masters and Johnson’s intimate relationship.

Dr. William Masters, Washington University’s foremost OB/GYN, runs a successful medical practice by day and conducts a secret study of human sexuality by night. Former nightclub singer Virginia Johnson joins the hospital secretarial staff and proves herself to be an asset to Masters’ work.

With Johnson no longer on his team, Masters accepts Libby’s offer to help compile the study work for a hospital-wide presentation. But when Masters sees another doctor’s presentation put his colleagues to sleep, he becomes determined to grab their attention even if it means pushing through provoking, but incomplete, research. Dr. DePaul and Johnson travel to a medical convention and DePaul opens up on why her work on the Pap smear is so important. And Virginia’s ex-husband George returns to find Ethan Haas playing father to his children.

Masters and Johnson decide that the best way to record their study findings is to film them, but to do so they have to enlist outside help. Johnson redoubles her efforts to get a college degree, only to find that Dr. DePaul’s Basic Anatomy class is a requirement. Meanwhile, Haas and Langham – both unsure in their relationships – convince each other of the merits of being a married man. And after Margaret catches him in a compromising position, Scully takes drastic steps to control his sexual impulses.

Masters and Johnson find their life's work in jeopardy. Season finale.

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.

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.

After Hendricks bans Masters from using black participants in his study, Masters contacts a journalist to promote his efforts, using the debunking of sexual stereotypes as the lure. Johnson is forced to accept DePaul's choice to end her chemotherapy treatments. Gene uncovers the truth about Betty and Helen's relationship. Libby fires Coral after discovering she lied about Robert.

After watching an early cut of the documentary, Masters is disturbed by the portrayal of his work. Johnson's move to solidify her custody arrangement with George backfires. Finding justification in Masters' distraction, Libby continues her relationship with Robert. Langham discovers Flo's family's wealth and connections, causing him to re-evaluate his relationship with her. And after repeated testing of their protocol to cure impotence, Masters and Johnson feel they are ready to cure sexual dysfunction.

Masters and Johnson look to capitalize on their burgeoning fame.

Johnson jets away with Dan Logan. Masters begins his surrogacy program.

Masters and Johnson turn to new partners in an effort to put the past behind them and focus on their expanding clinic. Given their fractured triangle, Libby reevaluates her relationship with Bill and Virginia.

Masters takes on a high profile patient. Virginia and Libby come to terms.

Masters and Johnson take on a famous couple hoping to renew their sex life.

In the wake of their fallout, Masters and Johnson search for purpose in a world without one another and look to work as their personal lives crash down around them. Libby finds herself alone for the first time since her marriage and discovers some unexpected allies. Season premiere.

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 objects to Masters' program following missteps in the protocol.

Masters begins a new job at Memorial Hospital under Betty's extortion terms only to discover that his boss insists he leave Virginia behind in favor of a handpicked secretary. Meanwhile, Johnson is torn between pressing Masters to rehire her and staying by DePaul's side as her condition worsens.

Masters looks to groom Art as his protege in a new area of research as Johnson does her best to keep Nancy at arm's length. Betty seeks an unlikely source for assistance in her fight for equal rights to Helen's baby.

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.