For three seasons, Lizzy Caplan and Michael Sheen have anticipated the sexual revolution as real-life sex researchers Virginia Johnson and William Masters in Masters of Sex, a fizzy mixture of fact and fiction.
As the show enters season four, which takes place as the 60s become the 70s, the world seems to have finally caught up with the prescient pair. Which may not rest so well.
"When we first met Virginia, it was 1956 and she had a very modern, ahead of her time way of approaching sex and her own sexuality," Caplan tells TimeOut. "Now it's the Swinging Sixties so everybody's bed-hopping and wife-swapping and going to key parties. I really think that would bother Virginia, she likes being a vanguard and so with everybody starting to catch up, there is a part of her that wants to tell everyone 'Well I did it first, so... don't forget that!'"
When we first encounter them in the new episodes, Masters and Johnson are separated from each other, both geographically and emotionally.
"Virginia's acting out in all kinds of ways," says Caplan. "She's drinking quite heavily now and she's also being really slutty, as only Virginia can, but what's interesting is as the world around her is starting to adhere to these more progressive ways of thinking, Virginia is now moving towards this more traditional idea of what she wants: marriage, commitment, all of that."
At the end of season three, Masters was locked up for solicitation. He too, begins the new season in a bad place.
"He's had to accept something: that Virginia doesn't love him," Sheen tells TimeOut in his native Welsh accent, rarely heard on screen. "And so at the beginning of season four, we see a man who has literally walked out of his life. He's just walked away from it all and he's going from motel to motel and drinking. He doesn't know who he is anymore or what he wants or what makes him happy. But he needs to have that time away from Virginia in a way, in order go through this kind of... transformation."
As you can probably imagine from the subject matter, Masters of Sex is never lacking for nudity. Caplan says it's something she's gotten more and more used to over time, but Sheen claims to have never had a problem with physical nudity.
"It's so much more exposing to do the emotionally vulnerable stuff," says the actor.
"Within the first week or something, Lizzy and I were doing sex scenes together, and I think we got very comfortable with each other and we created an environment on the set that made us feel comfortable. I do feel sorry for people who who are maybe just doing a day. There's one episode this season where there's a couple who literally all they had to do was come in, be naked, and have sex for about 10 minutes in the scene, while we're watching them. And that's hard."
When: Sunday, 8.30pm
What: Sex education