“Small Things Like These” plays just a little like a gangster film, except the web of power at its center is spun by nuns. Set in 1985 and based on Claire Keegan’s 2021 novel, it is a story about how people create and maintain control and the many shades of complicity that result. In this case, the setting is southeast Ireland, and the nuns’ control has woven its way into every aspect of life in a small town.

Bill Furlong (Cillian Murphy) sells and delivers coal and fuel in that town, an occupation that barely supports his wife, Eileen (Eileen Walsh), and a house full of daughters. But they’re doing OK. He can put food on the table, and they have a happy home life. One day, however, something changes inside Bill: He sees a young woman being nearly dragged into a building near the local convent, and it troubles him. He suspects that she is pregnant and unmarried, as his own mother was, and is being brought to the nuns by her horrified family. She is, quite literally, kicking and screaming. Bill can’t stop thinking about her.

Much of “Small Things Like These,” directed by Tim Mielants from a screenplay by Enda Walsh, happens in flashbacks. After Bill sees the girl at the convent, he drives home and notices a small, hungry-looking boy by the side of the road, and these two sightings seem to trigger some memory in him that he can’t shake. Even his wife notices his change in mood. It’s Christmastime, but the customary comfort and joy seem beyond him; instead, he keeps dissociating, slipping into a reverie about his own childhood. It wasn’t all sad: His mother was able to keep him with her, thanks to a kind employer, which meant that Bill was, in a sense, lucky. Yet, there were mysteries he never quite understood.

Murphy, fresh off his “Oppenheimer” Oscar win, is both producer and star of this film. His performance is unsurprisingly searing and nuanced, especially since Bill is not much of a talker. A lot of his performance is in extreme close-up, his panic showing up like lava pooling below a thin surface, ready to burst through at any moment. He has buried his grief and fear, but not nearly as far as he thinks, and the girl outside the convent has brought it all to a head. He’s a little bit like a synecdoche for his whole country.

Slipping inside the convent one day to deliver an invoice, Bill starts to suspect that the nuns, led by Sister Mary (Emily Watson), are mistreating the young women waiting out their pregnancies there. His dissociation turns into panic attacks, especially when he realizes there’s very little he can do to change the situation.

From the distance of history, it’s quickly obvious that this convent was one of the so-called Magdalene Laundries, institutions run by orders of Roman Catholic nuns as homes and profit-making laundry facilities. Text at the end of the film dedicates it to the more than 56,000 young women who were sent to the institutions between 1922 and 1998 for purposes of “penance and rehabilitation.”

The young women gave birth, then had their babies taken from them. They were forced to work without pay in conditions so wretched that some died. The acts committed at these institutions were so egregious that the Irish government apologized and established a National Centre for Research and Remembrance on the site of the last institution to close.

The Magdalene Laundries have been the subject of a number of films and series, including the Oscar-nominated drama “Philomena,” the Showtime series “The Woman in the Wall” and a number of documentaries. An appalling tragedy enacted on so broad a scale is hard to say anything new about once it has been uncovered; it’s hard to wrap your mind around.

So, the tack that “Small Things Like These” takes is less about the scale of the tragedy and more about a question that always arises when we consider this kind of cruelty. How could it happen? And why did it continue for so long?

There are simplistic answers, but none of them suffice. They are too black and white, and too disdainful of those who were around when the institutions were open.

Instead, “Small Things Like These” offers answers that feel more uncomfortable because they point back directly at us. Bill’s wife, for instance, tells him that “if you want to get on in this life, there are things you have to ignore.” Other townspeople warn Bill that probing what really goes on inside the convent could affect his own family. The nuns run the only school in town, after all, and Sister Mary is none too subtle about how hard it can be to get a place in the school. Like any organized-crime boss, she’s willing to slip money into hands in order to keep her operation running.

The message is clear: Abuse and violations of others’ rights only happen because the abusers make it extraordinarily difficult, and socially ill-advised, to expose their wrongdoing. This is a story often told, whether it’s about #MeToo or wartime atrocities or just turning away although we know something is not quite right. “Small Things Like These” asks, without giving a wholly satisfactory answer, if there is a way to confront ruthless power run amok. The only good response, it suggests, is to do the small, good thing.