Robert Harris had just completed a trilogy of novels about Cicero when he watched the election of Pope Benedict live on television. As a chronicler of power and its mutations, the scene — the Sistine Chapel smoke signaling a decision, of course, but also the whole, secretive tableaux — fascinated him. “Just before the pope comes out onto the balcony and reveals himself, the windows on either side fill up with the faces of the cardinal electors who had come to watch him,” Harris says.

“And the camera pans along the faces — elderly, crafty, cunning, some benign, beatific. And I thought: My god, that’s the Roman senate. That’s the old men running the whole institution.

I thought: There must be stories here.” That stoked Harris to write “Conclave,” a 2016 novel that went inside the Vatican to imagine how “the ultimate election,” as he calls it — with the added intrigue that the contenders must pretend they don’t want to win — might unfold. As page-turning as Harris made his novel, it might not have seemed the stuff of Hollywood.

A bunch of old men in robes sitting inside and picking a pontiff is not your average elevator pitch. But director Edward Berger’s adaptation, starring Ralph Fiennes as the cardinal leading the conclave, manages to be that rare thing in today’s movie industry: a riveting, thoughtful, adult-oriented drama acted out through dialogue by a sterling ensemble. “Yeah, we used to have ’em.

A lot. We don’t really have ’em.