Clutch the rosary beads, sister! Could there be a sinful scenario à la The Thorn Birds in the works on NBC's Revelations?

The Peacock's six-hour limited-run series, which begins April 13, features movie stars Bill Pullman and Natascha McElhone as a Harvard professor and a renegade nun who investigate omens that portend "the end of days," as predicted in the biblical book of Revelations.

They're like The X-Files' Mulder and Scully, only with the roles reversed. In this case, he's the doubting Thomas who seeks a scientific explanation for occult phenomena, while she's the true believer who's been dismissed as a blasphemous kook by authorities at the FBI, er, we mean the Vatican.

"Their relationship is unique," Pullman says. "It's not about coyness, it's not about some fabricated oil-and-water thing. They're two people with very different world views who are joined together. There's an intelligence about the way they deal with each other that you don't find that much in film scripts anymore."

And since McElhone's Sister Giuseppa is already on the Pope's poop list, we can't help but imagine that this wonder woman of the cloth is destined for defrocking by Pullman's Professor Massey. "Let's face it, there's never been a sexier nun on television and a more charming guy companion," teases Revelations writer David Seltzer. "But you'll have to watch the show. I am not going to do anything to bring the Vatican or anybody down on our heads!

"I frankly am so enjoying the growing familiarity and affection they have for one another," he continues, "and their ability almost to read each others' minds and realize that they are on a parallel course and are closer than they ever thought."

Just how close, though? "As for The Thorn Birds," Seltzer says, "I don't know that I would want to titillate you to think that it might happen — because it doesn't."

Not yet, anyway. If the ratings end up being a real Revelation, Seltzer hints that a regular series might result. Were that to happen, we foresee Sister Jo breaking that vow of chastity right around the time "the sun turns to darkness and the moon turns to blood" — or NBC needs a sweeps spike, whichever comes first.