Michael Sheen and Lizzy Caplan are "Masters of Sex"

LOS ANGELES – A series about science researchers in the 1950s would have a hard time finding an audience on PBS' "Nova." So what are its chances for success on Showtime, the network that brought you pot-dealing moms and serial killers?

High. That's because the featured clinicians in "Masters of Sex," which debuts Sunday, are William Masters and Virginia Johnson, the groundbreaking couple who addressed everything we ever wanted to know about sex, but were too repressed to ask.

For those who skipped sex-education class in high school: Masters was a renowned St. Louis gynecologist who became so obsessed with people's bedroom behavior that he started wiring up strangers in his lab and recording their reactions as they got down 'n' dirty. Johnson started off as his assistant, but later become both his writing partner and his wife.

That may not sound like must-see TV, but the series has plenty of factors that play well in the edgy world of pay cable, including steamy relationships, skeptical bosses, whorehouse visits and complicated characters, not the least of which is Masters, played by Michael Sheen.

The "Frost/Nixon" actor plays the doctor with so much restraint that it's hard to know what's churning inside his head and his heart. Is he truly watching people have sex as a cold, calculated experiment, or is he secretly getting turned on?

One of his study subjects nails it when he nicknames him Dr. Frankenstein.

"He's sort of a mystery to himself, really," said Sheen, who also signed on as a producer, in an interview this past summer. "He has so many locked rooms inside himself that he has to tread very carefully and make sure that he tries to control the environment so much. You might call it prudishness, but it's actually sort of a lock-down desire to keep control."

"I do feel like a lot of the women I've played leading up to this point have prepared me to play this woman who, I think, is by far the most layered and by far the toughest," she said. "I just have to sort of multiply the intensity of it all when placed in this time period, in this part of the country [Missouri], where she was not offered any sort of support for her more alternative decisions. You're not dirty for asking certain questions, and before Masters and Johnson, nobody was telling women that. It was always their fault. And that's some bull."

Despite the noble intentions of the actors, it's impossible to ignore the drama's third — and perhaps most prominent — character: S-E-X.

Much of the cast shucks their clothes on a regular basis and the cameras don't shy away from showing them pleasuring themselves or getting caught up in the throes of passion.

But creator Michelle Ashford, who based the series on Thomas Maier's 2010 book "Masters of Sex," said she banned any gratuitous sex scenes.

"I think that when you are watching a story, and then everybody just stops so you can watch sex for two minutes, it can seem really boring," she said. "One of the rules was the story always has to be pulling through the sex scene in some form. It has to be about something bigger than just watching people have sex."

Teddy Sears, who plays a subject, recalled a sex scene with actress Helena Yorke in which they wore so many wires that the set looked like a bird's nest.

"At one point we had to unspool them and do the whole thing over again," he said. "It gets decidedly unsexy after a while, but it was a lot of fun."