In Edward Berger’s “Conclave,” the selection of the pope is no holy affair. Instead, it’s a petty, political campaign carried out in secrecy, where gossip flows, agendas are malleable and loyalties are fleeting. All are there to serve God, they say. But we all know how helpful that has been in conflicts throughout history. “Conclave” might not have much new or interesting to say about the Catholic Church, but it is a deliriously fun watch in the way that tense, smart thrillers with an ensemble of great actors can be.

It’s fitting that Peter Straughan, who co-wrote the script for “Tinker Tailor Soldier Spy,” was the one to adapt Robert Harris’ 2016 novel, taking audiences inside the secretive halls of the Vatican in the immediate aftermath of the pope’s death. The film opens abruptly and effectively on Ralph Fiennes’ back, walking somewhere briskly. Nothing is said. You don’t even see his face. But between Volker Bertelmann’s heightened score and Fiennes' pace and tensed shoulders, the mood is set. This, it is clear, is not going to be a straightforward affair. Plus, something seems a little fishy about this death.

Fiennes plays Cardinal Thomas Lawrence, the dean of the College of Cardinals, whose duty is to oversee the election of the next pope. That means gathering a group of 100-some clergymen in Rome to vote. With many dreaming of ascending to the position, they’re secluded from the outside world and left to their own devices to lobby for support.

There are some formidable forces at play following the death of a more liberal-minded pope. Stanley Tucci’s Aldo Bellini is a progressive hoping to evolve the church dramatically. Sergio Castellitto’s Goffredo Tedesco thinks they’ve gone astray and wants to bring it back to the days of Latin Mass and Italian leadership. There’s also Lucian Msamati’s Joshua Adeyemi, from Nigeria, who stands to make history as the first Black pope but whose views on homosexuality worry the progressives. And finally, John Lithgow’s slick but earnest Joseph Tremblay, who, unlike Bellini, wears his ambition on his sleeve. He also happened to be the last official meeting on the pope’s schedule before he died and delayed before calling Lawrence with the news.

In a film business where youth still reigns supreme, “Conclave” is a symphony of lovely aging faces. These actors whose forehead lines don’t disappear at rest are in full command of their instruments showing a world of experience, doubt and regret in any given glance. Fiennes gets the majority of the close-ups, as a man who is having to manage this increasingly unwieldy proceeding while also grappling with his own internal crisis. He reveals to Bellini, who he hopes will be selected, that he recently attempted to resign. His request, he said, was denied.

And now he’s left dealing with a bunch of babies in a conclave that is stretching on longer than anyone would like. There are rumors of a withdrawn report of gross misconduct, a sabotage plot and the surprise arrival of a cardinal no one knew existed: Carlos Diehz’s Vincent Benitez, who was secretly appointed archbishop of Kabul. With turmoil both on the streets and inside their claustrophobic and gossip-ridden surroundings, everyone is going a little mad wondering if they’ll have to simply settle for the least worst choice. Even Isabella Rossellini’s head nun, who is supposed to be a silent participant, gets involved (thank goodness for us).

Berger, a German-Austrian filmmaker who last made the stunning adaptation of “All Quiet on the Western Front,” keeps the audience on the edge of their seats for the duration as you try to piece together the clues to figure out who is holding the strings. The specific setting of the Vatican adds mystery and dramatic flair — the filmmaker seems to take great pleasure in the elaborate and frequent costume changes and ceremony of it all — but this is also a classic story that could have easily been set near any seat of power. “Conclave” is sure to ruffle some Catholic feathers — provocation is in its DNA. But for the rest of us, this juicy, smartly crafted thriller, is simply a great watch.

“Conclave,” a Focus Features release in theaters Friday, is rated PG by the Motion Picture Association for “thematic material and smoking.” Running time: 120 minutes. Three and a half stars out of four.