The many unattractive faces and personality traits of deeply flawed humanity cross the screen in “The Ugly,” a Korean murder mystery and human nature parable from the filmmaker of the zombie thrillers “Train to Busan,” “Seoul Station” and “Peninsula.”

It isn’t the undead who are hideous in this one. It’s petty people lacking self-awareness and — to bend Hannah Arendt’s most infamous phrase — “the banality of cruelty” that writer-director Sang-ho Yeon holds a mirror up to.

Yeong-gyu (Hae-hyo Kwan) has been a fixture in his Seoul neighborhood for decades. He’s a blind artisan who gives the lie to the “misconception” that “the blind” have no idea of what consistutes “beauty.”

Yeong-gyu carves lovely, tiny embossing stamps with a person or business’s name on them, using just his fingers to spell out and shape the Korean language characters. He and his small shop have been the subject of feature stories and TV profiles over the years. We meet him as another perky, persistent TV producer (Ji-hyeon Han) is questioning him and the sighted, 40ish son (Jeong-min Park) who has taken over the business.

But the lightly inspiring feature story the TV gang has in mind takes a turn when son Dong-hwan gets a call from the police. They’ve found his mother’s body. Dad always told him that mom “ran away” from them. Now bones, buried on a nearby hillside, reveal her fate forty years ago. Or some of it.

The ugliness starts at the funeral, where Dong-hwan and producer Kim are abruptly subjected to surviving members of his mother’s family. They are rude and blunt about the “inheritance” he won’t be getting. His mother “stole jewelry” when she fled the family, they say. As a cruel kicker, they mention that no there are no photographs of the late Yeong-hee and for good reason. .

“She was ugly,” the most callous aunt to attend declares, in Korean with English subtitles.

The family who hated her and the blind husband who may have lied about why and how Mom “left” are the first two suspects in what becomes the new focus of the TV crew’s documentary — “Who killed Yeong-hee?” The dazed and grieving Dong-hwan is dragged along as he’s too polite to demand one and all back the hell off while he mourns and absorbs all he learns.

They meet former co-workers and Mom’s old boss, with producer Park smiling and questioning one and all and secretly recording the interviewees. Dong-hwan would never have found these people without the resources of the TV journalists. But he’s haplessly caught up in this sketchy “secret” taping, forced to pass himself off as a disinterested “writer” on the show while one tactless creep after another trashes his mother, her appearance and who had a reason to kill her.

Lengthy flashbacks take us back to the ’70s sweatshop where Mom worked, taunted by colleagues with the nickname “Dung Ogre” and ill-used by one and all. Only one person who “knew her when” seems the least bit remorseful about how she was treated and her final fate.

It isn’t the “mystery” that writer-director Sang is most interested in, it’s the Korean manners and mores battered with every turn in this story, beginning with the callous family members’ obscene treatment of the long-lost nephew they couldn’t wait to visit so that they could insult his long-dead mother.

The change in Korea’s fortunes and place in world capitalism is addressed in the flashbacks. And there’s an implicit damnation of shifting standards of beauty and “ugly,” with Korean “inferiority” complexes playing into that in ways that “Joy Ride” made fun of. Perhaps Sang, who wrote the graphic novel “The Ugly” is based on, has a favorite “Twilight Zone” episode in the back of his mind, too.

Park makes a poker-faced leading man, rarely giving away the emotion and fury Dong-hwan must be feeling as he faces every new humiliation thrown his dead mother’s way. There are hints of a cultural reserve that his character embodies, with almost everyone else crossing cruel and tactless lines, being brutally blunt in ways few decent human beings would.

The flashbacks have a melodramatic brio that the present-day scenes lack, showing us stakes and a “Rashomon” collection of possible fates the dead woman faced.

As parable, “The Ugly” isn’t wholly satisfying as it passes judgement and merely hints at the psychic and cultural cost of mob mentality cruelty, perhaps a consequence of Korea’s rush to modernize and make a quick buck.

But it’s great that Sang found another way to chew on the facets, faces and foibles of his native land, one that didn’t involve ravenous zombies.

Rating: unrated, violence, nude photographs, sex-crime subject matter, smoking

Cast: Jeong-min Park, Hae-hyo Kwan, Ji-hyeon Han, Hyoen-bin Shin and Sung-jae Im

Credits: Scripted and directed by Sang-ho Yeon, based on his graphic novel. A Well Go USA release.

Running time: 1:43