“Freud’s Last Session,” starring Anthony Hopkins as Sigmund Freud, adds to a string of sterling late- chapter performances by the 86-year-old actor. He was the soul of “Armageddon Time,” the reason to see “The Father” and the papal foil to Jonathan Pryce’s Pope Francis in “The Two Popes.” With the exception of James Gray’s more cinematically composed “Armageddon Time,” the movies have offered simple, stagy showcases for Hopkins, a lion in winter.

“Freud’s Last Session” also comes from the stage and, like “The Two Popes,” centers on the tete-a-tete of intellectual opposites. Mark St. Germain’s 2009 two-character play brought together Freud and C.S. Lewis (played by Matthew Goode in the film) for a speculative meeting between the two in 1939 London.

An aging Freud, suffering from cancer, prepares to receive the Oxford academic at his London home while war with Germany grows inevitable. The factual jumping-off point is that Freud, three weeks before his death, is recorded as meeting with an unnamed Oxford don. As Freud’s daughter Anna (Liv Lisa Fries) prepares to leave in the morning, he mentions Lewis’ impending arrival. “The Christian apologist?” she responds. “Yeah,” he chuckles.

Their conversation, which makes up the bulk of the film, imagines a spiritual debate between the father of psychoanalysis, a proud atheist and man of science, and the theological Lewis, a believer who in the years after “Freud’s Last Session” takes place would pen his Christian apologetic novel “The Screwtape Letters” and, later, the parables of “The Chronicles of Narnia.”

If their adverse positions didn’t make for enough drama, air raid sirens are sounding (Hitler has just taken Poland) and Freud’s health is bad enough that he eyes a suicide pill several times during the day. Death and history buffer their talk of God, fear and pain.

But the elements never quite cohere in “Freud’s Last Session.” The rhythm of conversation is choppy and lacks the probing give-and-take that can electrify a two-hander. Freud dominates their talk. Goode remains more removed for his Lewis to ever fully engage Freud.

Director Matthew Brown, who shares screenwriting credit with St. Germain, has artificially “opened up” the play to include flashbacks and side plots, most notably that of Anna, whose devotion to her father factors into Freud’s discussions of sexuality. Yet Anna’s story, including a relationship with a woman, not acknowledged by her father, is too complex to graft into the theological debate. It feels like a movie in its own right. That “Freud’s Last Session” is overly murky also contributes to the movie’s lack of clarity.

But Freud and Lewis’ dialogue finds compelling points of commonality. Fantasy figures prominently into both minds — Freud in his analysis of dreams and Lewis in the dreamworlds he’ll create. And both come to their beliefs in part from childhood experiences that color their lives.

And Hopkins remains riveting. Some three decades after memorably playing Lewis, himself, in 1993’s “Shadowlands,” he now plays across from the novelist, adding to the poignance of the movie.

But I suspect my memory will bleed together some of Hopkins’ late films. In each, he grapples with a life of accomplishment, just as he presents pains and joys. Each performance crackles with wit, wisdom and playfulness in the face of the inevitable.

MPA rating: PG-13 (for thematic material, some bloody/violent images, sexual material and smoking)

Running time: 1:48

How to watch: In theaters