The new season of Masters of Sex will find William Masters (Michael Sheen) and Virginia Johnson (Lizzy Caplan) getting new partners both professionally and personally, something that the stars say will be quite an adjustment for their characters.

The new dynamic will be particularly tough for Masters, who at the end of season 3 lost both his wife (Caitlin FitzGerald) and the woman he loved in Johnson. “When we find them again this season, he’s smarting pretty hard from that and is working double time to protect his heart from this woman who has an uncanny ability to smash it into a million pieces over and over again,” says Caplan in the video above.

While Masters is trying to rebound from the loss of Johnson, Sheen says that he must navigate how to coexist with her under these different circumstances. “Obviously, Virginia comes back into his life, so now he has to try and find a new way to be with her that goes against all his instincts,” he shares.

Not only will the characters be dealing with a change in relationship status, but also in a change of eras. The show originally began in the traditional, buttoned-up ’50s but will shift to the radical ‘70s as season 4 progresses, an adjustment for both Masters and Johnson.

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“Well, we’re moving into the end of the ‘60s, into the ‘70s now, so we start to see them in situations like there are swinger parties and there are nudist colonies,” says Sheen. “So the world is changing around them, partly because of them, and they’re now having to interact in that, so the situations they find themselves in are by necessity kind of surprising and different and strange.”

Masters of Sex returns to Showtime on Sunday.

— Additional reporting by Robyn Ross

Episode Recaps

Masters of Sex

This Showtime drama tells the steamy story of real-life sex researchers in the 1950s.

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