Masters of Sex season 4
Masters of Sex season 4 premieres 11 September on Showtime Showtime

Michael Sheen and Lizzy Caplan return as real-life pioneers of human sexuality, Dr William Masters and Virginia Johnson in season 4 of Masters Of Sex. The fourth season will pick up in 1968 and take viewers into the "swinging '70s" during which time the characters will take on new partners both professionally, personally and sexually.

Episode 1 is titled, Freefall, which airs on Sunday (11 September) at 10pm ET/PT on Showtime. The official synopsis of the premiere episode reads as follows:

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.

Click here to watch the episode online. You can also click here to watch it live on Showtime Anytime only in the US.

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Actors Danny Jacobs, Stephen Root and Romy Rosemont will guest-star on the fourth season of Showtime's drama. Executive producer Michelle Ashford spoke to Moviefone about Masters Of Sex season 4 and shared details about the show's opening scene.

She said, "We start this season with Virginia Johnson sitting in a hotel room watching this protest in the Miss America pageant in 1968 where women are just outraged and traipsing along the Boardwalk in Atlantic City with a sheep with a crown on its head and throwing their bras into trash cans."

Ashford revealed that every character will go through a "great transformation" and added, "It's such a curious moment because she was always such a radical really in many ways, and now the world has not only caught up, but surpassed her because she likes her bra. We really thought, 'Wow, this is a really energizing time!' Every character is undergoing great, great transformation."