Chinonye Chukwu’s “Clemency” opens with a sequence that’s hard to watch, but impossible to look away from. A prison warden, Bernadine Williams (Alfre Woodard) steadies herself and readies her team for an execution. They strap the inmate sentenced to death to a table and administer a series of fatal drugs as his family looks on from behind glass. But the drugs don’t work. The inmate panics. The warden scrambles. She’s got a job to finish.

The nature of Bernadine’s job is at the center of “Clemency,” a brutal and beautiful meditation on the reality of death and the barbarism of state-sponsored execution. When confronted with the inhumanity of the death penalty by defense lawyers, advocates and inmates on death row begging for their lives, Bernadine falls back again and again on the task at hand. She’s just doing her job.

But this job has sapped Bernadine, too, the life drained from her eyes. She’s a zombie of sorts, shuffling through life from work to the bar to home and back again. Bellied up to the bar with a scotch in hand, she’s at ease debating the legal justifications of her ugly responsibilities as a prison warden who imprisons and kills men for a living. But she’s uncomfortable at home, wracked by nightmares, unable to connect with her loving husband (Wendell Pierce), a high school teacher who wants nothing more than to make their marriage work. He works to live, while she lives to work, a dirty dehumanizing work, but someone’s got to do it.

The conflict at the center of “Clemency” isn’t just Bernadine’s existence, but her relationship with one of her death row inmates due to be executed, Anthony Woods (Aldis Hodge), waiting for salvation from the courts. His lawyer (Richard Schiff), worn down by the case, swears off this kind of work for good after Anthony’s fate is decided. Hodge is stunning in a tender, wild-eyed, yearning performance. Anthony, wavering on a thin line between life and death, grasps at any shred of agency he can. He offers an emotional foil to Woodard’s methodical Bernadine, and the scenes where she mechanically performs the rituals of government-sanctioned murder (“last meal?”), as he mourns his life in advance of his death, are devastating.

But Bernadine receives her own comeuppance, and Woodard, who has so deftly controlled the cracks and ripples in her emotional armor, lets it all flow out. Her performance is nothing short of masterful, a study in restraint and control, and when the shield comes down, it is a gut punch. Control and restraint are the main themes of the film’s story, and are reflected both in the performances and in Chukwu’s austere and unflinching filmmaking.

Chukwu wrote the script, an exercise in contained storytelling, and creates a cinematic form that is a prison itself. The locked-off camera stays rooted in place on faces for extraordinarily long amounts of time, capturing every emotion that flickers or roars across the faces of people in the most despondent moments of their lives. The camera, positioned right above the executioner’s table, captures these characters at the ends of their lives, and their emotional journeys in these final moments reassert their humanity after it’s been denied for so long. Chukwu affords this humanity even to her angel of death, Bernadine, in these final moments too, in a gesture both generous and damning.