Dr. William Masters, a successful doctor of obstetrics and gynecology, begins his controversial study of human sexuality. Dr. Masters recruits Virginia Johnson to be his secretary, but she quickly advances to be a valuable associate.
The Provost shuts down the research when he hears about the couples study and Masters is forced to move it elsewhere. Dr. Masters blames Virginia and fires her, but keeps her on until he can find a replacement.
A woman pregnant with quadruplets comes to the hospital and Dr. Haas lobbies for the case. A female gynecologist joins the staff. Both Dr. Masters and his wife learn a secret and both get what they want.
Both Bill and Virginia have unexpected and unwelcome visitors at home. With the study back in the hospital, new participants are recruited. Ethan struggles to forget his feelings for Virginia.