A pope dies and over 100 of his archbishops gather to politic, poor-mouth, backbite and backstab their way towards electing another in “Conclave,” a deliciously dark, well-acted and beautifully-filmed inside-Vatican-intrigues thriller.

Director Edward Berger (“All Quiet on the Western Front”), with screenwriter Peter Straughan adapting a Robert Harris novel, serves up a sumptuous pageant of ritual and tradition as the red-robed archbishops — captured with their whiter-than-white umbrellas in the Vatican City rain at one point — meet and vote, scheme and investigate, form alliances and wrestle with issues of faith, “liberalism” and a “Universal Church” that is losing favor and losing ground around the world, if not on the “stacked” U.S. Supreme Court.

It’s a thinking filmgoer’s film, and a darkly comic one as it exposes the mere mortals who act all too human as members of the ultimate elite, a gathering of serene majesty and self-importance, one almost guaranteed to tumble into melodrama.

Ralph Fiennes is Archbishop Lawrence, Dean of the College of Cardinals and one of the innermost inner circle at his bedside when the pope dies. He had hoped to resign from this position and take up his ongoing struggle with “belief” in a monastery or some such. Or so he keeps saying.  But he is “a manager,” the dead pope once told him. “Managers manage.”

That’s just what he is to do when the archbishops from near and far, some 108 of them, descend on Rome to pick a new pope, “sequestered” from the world, voting on paper ballots that are then burned after each round of voting until white smoke spills out of the chimney of the Sistine Chapel, telling the world that they’ve reached a decision.

It will take a two-thirds majority of archbishops to make that secret ballot selection, with all the ballots burned — evidence — letting the world believe something like a full consensus has been reached.

Lawrence is aligned with the liberals, like the just-passed-pope. They’re rallying around the American Aldo Bellini (Stanley Tucci). But the politicking Tremblay (John Lithgow) is playing the angles, out to grab the papal regalia and power for himself.

An archbishop from Africa (British TV star Lucian Msamati) is a popular choice among third world clerics.

And then there’s the conservative, chain-vaping Italian Tedesco (Sergio Castellitto of “Mostly Martha”) who’s of the Mel Gibson “Latin Mass,” take the church back to the pre-“Second Vatican Council” ultraconservative school, someone who “must be stopped,” the liberals all agree.

The dean must keep the peace and maintain the church’s image during this possibly fractious conclave. But right from the start, he’s tipped about the old pope discovering corruption in one of the candidates. The liberals’ agreed-upon champion Bellini insists he is “not fit” and has no interest in the papacy, even as he trots out the word “ambition” to decribe anyone who might stand in his way.

And a new “secret” archbishop has arrived and must be investigated, at least superficially, before he can be seated. Archbishop Benitez, played by screen newcomer Carlos Diehz, was appointed in secret and kept secret afterwords. Lawrence’s right-hand-man, bishop O’Malley (Brian F. O’Byrne) can’t find much about him. Maybe the pope kept this archibishop secret because of Benitez’s posting.

He is archbishop of Kabul, Afghanistan, right in the murderous heart of the most intolerant corner of Islam.

Isabella Rossellini plays the nun in charge of the army of churchwomen who work to keep this conclave fed, laundered and doing its duty. But scandal, scheming and petty mistrust writ large with the stakes so high threaten to upend it all.

“Although we sisters are supposed to be invisible, God has nevertheless given us eyes and ears.”

And outside, we hear, there are protests and bombings. Over what is never made clear.

The Oscar-winning Fiennes is in great form playing a conflicted man who must maintain decorum, and his temper, in the face of myriad challenges. He practically crumples his crucifix in fury at the end of each day’s test.

It is to the credit of the entire supporting cast that one and all hold his or her own with Fiennes and his magnificently internalized seething.

Tucci, Lithgow, O’Byrne and Rossellini each have their best roles in years and don’t disappoint. Casteillitto, Diehz and Msamati impress.

And Berger gives this all the kind of gravitas it deserves — a new church “direction” in a world turning away — even as he is letting in just enough air that the faithful and those critical of “The Church” can have a laugh at the arcane pageantry and human vindictiveness that all the pomp and circumstance in the world can’t paper over.

“The men who are dangerous are the ones who want it!”

I can’t stress enough how beautiful the images here are — crisp costumes in pristine settings embracing the ancient history, high art and timeworn rituals of this world and this process. The settings are striking and overwhelming, the shot selection, lighting and blocking are perfect.

A few films have taken us into the regal papacy under such conditions, with the 1968 epic “The Shoes of the Fisherman” being the first and most impressive that I recall. That film was a pre Pope John Paul appreciation of the Catholic Church’s position in the Cold War. In “Conclave,” it’s a reeling institution that can ill afford one more scandal after decades of bad press that is depicted, a church whose top tier officials ponder their faith and the buy-in that involves.

The finale turns dramatically melodramatic, suggesting the severest trial will produce the most radical changes and revealing who the most cunning manipulator of all might be. It’s enough of a jolt that you may laugh at the audacity of it, or the incredulity.

But “Conclave” is a deliciously immersive experience, a narrative that commands our attention and expects our speculation even if it maintains a distance that allows it all to seem out-of-step, surreal and even darkly humorous at its most extreme.

Rating: PG

Cast: Ralph Fiennes, Stanley Tucci, Isabella Rosselini, John Lithgow, Lucian Msamati, Sergio Castellitto, Carlos Diehz and Brian F. O’Byrne.

Credits: Directed by Edward Berger, scripted by Peter Straughan, based on a novel by Robert Harris. A Focus Features release.

Running time: 2:00