In previous roles as Gandalf, King Lear and Macbeth, Ian McKellen commanded stages and screens with a voice that could make walls shiver. He was Shakespearean, mythic, untouchable. These roles required a man to tower, to be something more than human.

Now 86, Sir McKellen’s latest character, Julian Sklar, stares down at a bathtub in silence. In it, hidden under a stained tarp, lie eight sepia paintings of a man’s face, half-turned and half-finished. They are the only remnants of a love that once consumed him: a series of paintings of his former lover dubbed the Christophers.

In Steven Soderbergh’s new movie “The Christophers,” released April 10 and now in theaters, Ian McKellen delivers one of the most powerful performances of his career, made possible by the containment of his usual grandeur. 

Though still a relatively famous artist, Julian is starting to fade from public memory. Aged and terminally ill, he has not created any new art in decades. He spends his hours recording Cameos for overeager fans. 

Michaela Coel plays Lori Butler, an art restorer secretly hired by Julian’s children to finish The Christophers so they can be sold upon their father’s death. Julian, who has spent decades curating his own mythology, sees something in Lori that he has lost: authenticity. Ms. Coel —  equally terrific in her role — portrays a character who refuses to perform for Julian, quick to walk out when insulted and unwilling to offer empty compliments. Even as she lies about her intentions her affect remains honest. But, unlike Julian, she chooses to endure the art world rather than retreat from it.

What is especially extraordinary about Sir McKellen in “The Christophers” is precisely that his performance thrives on the ordinary. His rasping voice is softer, cracking slightly as he recounts his losses. Though the master of the monologue has been confined to an apartment set rather than a stage, the sonority remains. 

“The Christophers” centers around an aging artist who was phenomenal in their prime but has started to lose attention. It’s a concept that cuts terrifyingly close to Sir McKellen himself who has lived his life in theaters and dedicated himself to epics. Now Sir Mckellen has chosen a role that poses a different question: What happens when the curtain doesn’t fall on your terms? What, then, do you become?