With the study back in the hospital, Masters and Johnson recruit new participants on campus. But Johnson is shocked when her ex-husband George, who’s crashing on her couch, wants to sign up. Masters’ mother comes to visit, but her new take on life stirs up painful memories of his childhood. And Libby’s attempt at playing matchmaker with Virginia and Ethan doesn’t go as smoothly as she’d hoped.

When Masters and Johnson expand the study to include couples, they discover that the science of sex is easily complicated by the mystery of attraction. Johnson tries to connect with her son who prefers his dad. In anticipation of his baby’s impending arrival, Masters experiences anxiety about becoming a father. And Dr. Ethan Haas learns that dating the provost’s daughter could impact his medical career.

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.

Masters deals with the ramifications of his disastrous presentation and being fired from the hospital. Meanwhile, Libby urges Masters to get another job; and Virginia fights off advances and innuendos stemming from the belief that she was the woman in Master's explicit film.

In the wake of Masters' discovery that Johnson has continued to have romantic relationships with other men, he becomes impotent without her knowledge and cuts off their sexual work together. He tries to keep his new clinic solvent over the course of three years by borrowing against his house, offering medical services to the hotel - and finally accepting money from his mother.

Virginia continues to impersonate a patient's case history in order to glean advice from a psychiatrist. Betty and Masters' attempt to remedy Lester's impotence by hiring a prostitute rattles him even further. Libby gets the third degree when she offers her eyewitness testimony regarding the beaten man. And Barbara Sanders wrestles with an unsettling diagnosis that exposes a chain of secrets and causes Masters and Johnson to clash over their treatment strategy.

Masters learns of a rival study and calls in a public relations expert to help brand his work with Johnson. Virginia, having finally learned of Masters' sexual difficulties, is invigorated by the prospect of finding a cure. Determined to prove her worth to Robert, Libby canvases a tenement for a rent strike. Plus, Langham is stunned when Flo informs him that he has to have sex with her in order to keep his job. And Barbara and Lester connect over their shared sexual dysfunctions.