Masters and Johnson continue their research in the brothel but skewed data confirms that Masters must get the study back into the hospital. At the hospital, Johnson is surprised to learn that a distinguished new doctor on the OB/GYN floor is a woman who has no interest in female solidarity. Meanwhile, Libby struggles to conceive and Dr. Ethan Haas gets the case of a lifetime – a woman pregnant with quadruplets.

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.

The hospital takes part in a nationwide civil defense drill, and the heightened atmosphere escalates conflicts among the staff. A former study participant reveals she’s pregnant and wants to know the identity of the father. Masters and Johnson, their relationship strained after ending their study participation, butt heads on whether to maintain study confidentiality or take responsibility. Haas learns he’s been denied a future job at the hospital but wrongly assumes his breakup with Vivian is to blame. Margaret Scully seeks answers about her husband’s sexuality from an unlikely source.