The new prison movie “Sing Sing” begins with a glorious, if short-lived, escape. There are no secret tunnels, no stolen cellblock keys. At Sing Sing Correctional Facility, in Ossining, New York, a spotlight shines down not on a yard lined with barbed wire but on a stage bathed in radiant blue. The play is “A Midsummer Night’s Dream,” and the actors, all men, are participants in a program called Rehabilitation Through the Arts, or R.T.A. For them, the chance to wear glittering costumes and ride the giddy waves of Shakespeare’s verse promises a few hours of liberation.

One performer, John (Divine G) Whitfield, played by Colman Domingo, seems to capture the fleeting nature of the experience with some of Lysander’s most famous lines: “And ere a man hath power to say ‘Behold!’ / The jaws of darkness do devour it up; / So quick bright things come to confusion.” So quick is right. All too soon, the men have changed back into their green uniforms and returned to the daily tedium and terror of incarceration. The vastness of the stage, with its lofty view of a noisily appreciative crowd, gives way to the confines of a cell, so hushed and sealed off that it might as well be buried underground.

The walls of Divine G’s cell, covered with documents, photographs, and sticky notes, are evidence of a term spent in thrall to the written word. While serving out his sentence—twenty-five years to life for a murder that he didn’t commit—Divine G has devoted much of his time to studying law, researching his case and those of other incarcerated men, and seeking solutions that might expedite their release. He has also written several novels and plays, which have earned him a measure of fame among his peers; some of his plays have even been staged by R.T.A., of which he is a founding member. One of the many grace notes of Domingo’s performance is that, beneath Divine G’s warm modesty, we discern a glimmer of pride in his position as the prison’s resident literary titan and legal expert. The movie does not begrudge him his self-importance.

All this springs from true events. The director Greg Kwedar, who wrote the script with Clint Bentley, first encountered his protagonist in a 2005 Esquire article, “The Sing Sing Follies,” by John H. Richardson. Domingo’s Divine G is a stand-in for the real-life Whitfield, who receives both a story credit and an amusingly flattering cameo in which he basically gets to ask his younger self for an autograph. Whitfield is not the only cast member who spent years at Sing Sing. The ensemble features multiple alumni of the prison’s R.T.A. program playing versions of themselves; several of them, including Mosi Eagle, Dario Peña, and David (Dap) Giraudy, appeared in Richardson’s piece.

As we watch them mount their next production, helped by a director from the outside named Brent Buell (Paul Raci, the superb character actor from “Sound of Metal”), their cycles of preparation—acting exercises, auditions, workshops, rehearsals—have the ring of an artfully reimagined truth. The cinematographer Pat Scola deploys an often handheld, gently agitated camera, sometimes recording these rites from a distance, sometimes moving in for a more dramatic look, and at all times conferring an air of unshakable authenticity.

These realist inflections belie a charmingly cornball story. Kwedar and Bentley previously collaborated on the tough-and-tender equestrian drama “Jockey” (2021), and here, as in that film, they can’t resist an old-fashioned redemption arc, replete with hard luck, perseverance, and a sentimental finish. In “Sing Sing,” the tale gets under way when Clarence (Divine Eye) Maclin (played by himself), known for his temper even in a world where hostility is the norm, signs up to join R.T.A. Others in the program have their doubts, especially after a tense prison-yard confrontation in which Divine Eye, who deals drugs, shakes down an underling for money. But Divine G is inclined to give him a chance, perhaps sensing that beneath the puffed-up aggression is a natural ham. (Divine Eye’s sly way with a “King Lear” reference doesn’t hurt.)

This act of magnanimity has unintended repercussions. It is Divine Eye who scuttles plans to produce Divine G’s latest work in progress and suggests that R.T.A. put on a comedy for a change (an admittedly odd request, so soon after “A Midsummer Night’s Dream”). And so Brent writes “Breakin’ the Mummy’s Code,” a sprawling, time-travelling farce that tosses together elements of Egyptian mythology, the legend of Robin Hood, “A Nightmare on Elm Street,” and “Hamlet”—and, in a richly Shakespearean irony, it’s the gifted newcomer, not the seasoned veteran, who gets cast as the Prince of Denmark. Despite these initial dustups, the two Divines genuinely come to love, respect, and support each other; Divine G eventually offers to assist Divine Eye in preparing for a parole-board hearing, even as his own bid for clemency goes nowhere. Their blossoming friendship gives “Sing Sing” an irresistible emotional hook; it would take a more stoic viewer than I to hear one man call the other “Beloved”—the R.T.A.’s preferred term of brotherly endearment—and not shed a tear. But the insistent feel-good trajectory comes at the expense of thornier truths. The movie, for all its understanding of hard time, can’t keep from going a little soft.

Founded at Sing Sing in 1996, and now operating at eight correctional facilities across New York State, Rehabilitation Through the Arts is one of several theatre programs that have set out to transform prisons and the imprisoned from within. Its mission is to help incarcerated people develop life skills, build self-esteem, and express their emotions, as well as nurture artistic talents. If the outlines of “Sing Sing” sound familiar, it’s surely because such programs have provided filmmakers with no shortage of inspiration—and also the opportunity, in theory, to rejuvenate the subgenre of let’s-put-on-a-show movies with shades of moral ambiguity and real-world gravitas.

The year 2009 brought us both Zeina Daccache’s documentary “12 Angry Lebanese,” about a production of “Twelve Angry Men” inside Beirut’s notorious Roumieh prison, and Davide Ferrario’s musical “Freedom,” about a Passion play staged by prisoners in Turin. Perhaps the best known of the lot is “Caesar Must Die” (2012), directed by the Italian brothers Paolo and Vittorio Taviani, who took us inside the maximum-security wing of Rome’s Rebibbia facility. Shooting their subjects in stark black-and-white, the Tavianis raised—but also complicated—the notion that these grave-faced men, imprisoned for violent and often Mob-related crimes, might have a unique understanding of “Julius Caesar,” with its vision of murder as a meticulously planned, collectively organized activity. Others may recall the 1987 drama “Weeds,” starring Nick Nolte as a robber whose plays, written and staged behind bars, secure him release from a life sentence. Pauline Kael, reviewing the film in The New Yorker, wrote that it “never goes very far into the issues it raises, but the messy collision of energies keeps a viewer feeling alive.”

Much the same could be said about “Sing Sing,” which is propelled by an ensemble that veers between conflict and camaraderie; we are kept off balance by Brent’s sharp, tough-love direction, Divine Eye’s instinctive wariness, and Divine G’s mounting despair. Even so, the movie is too neatly divided between the teeming, textured world it’s re-created and a narrative that never moves past the sturdily conventional. I wouldn’t have minded a few messier collisions, or a deeper engagement with some of the Divines’ fellow-actors. We never learn much about their backgrounds, and though there’s a certain integrity in that omission—a refusal to let these men be defined by the crimes of which they were rightly or wrongly convicted—there is also a certain incuriosity that undermines the film’s bid for authenticity. You come away from “Sing Sing” wanting more of the characters, more of their lives, and more of their creative processes; it’s a shame that we see only a few amusing snippets of “Breakin’ the Mummy’s Code,” which looks like a welcome hoot, if nothing else.

Having pared away nearly every detail that doesn’t advance the plot, Kwedar and Bentley rely heavily on their lead actors to fill the ensuing breach. In this, at least, their instincts are sure: it’s no surprise that Domingo, coming off his boisterous, Oscar-nominated star turn as the civil-rights leader Bayard Rustin, is so persuasive as a man with a gift for teaching and inspiring others. But the discovery here is Maclin, who seems altogether unbeholden to the younger version of himself described in Richardson’s piece: “Divine Eye has long dreadlocks and massive muscles and sings ‘Happy Birthday’ with showbiz pizzazz.” The movie’s Divine Eye is made of sterner, balder, less musical stuff; he bullies, extorts, and hurls threats at the slightest provocation. By the end, though, he has become an artist of remarkable confidence, a friend capable of receiving and returning compassion—and, above all, a man with a profound understanding of what to be and not to be. ♦