A deep bow of respect is due to Ms. Joey King, who used her newly emerging star clout (“Fargo,” “Kissing Booth,” “Slender Man,” “Summer ’03”) to get “Radium Girls” on the screen.

It’s a well-acted, smartly-reported and heartfelt if somewhat malnourished period piece about the heroic women of U.S. Radium Corp’s New Jersey watch-dial factory. In the mid-1920s, they realized they were being poisoned, painting luminous radioactive numbers on watchfaces, and took the callous corporation to court, exposing a cover-up that changed American labor and workplace safety.

Reminding people of the Radium Girls‘ sacrifice and struggle at a time when worker rights and worker safety are under open assault is a gutsy move and does a great credit to King and co-star Abby Quinn (“Little Women,” TV’s new “Mad About You”).

Filmmakers Lydia Dean Pilcher, Ginnhy Mohler and (co-writer) Brittany Shaw tell a compelling, old-fashioned story in a somewhat stolid (corny, even) style. But the leads, playing sisters employed at the factory, make us care and break our hearts in this classic tale of Big Business lowballing the value of human life and sacrificing worker safety in the process.

Bess (King) is a 17 year-old who dreams of silent screen fame, like her idol, Rudolph Valentino. Older sister Josephine (Quinn) is the smart one, and the industrious one. She turns out many more dials per day, because like the other workers at American Radium, she licks her brush to keep its point fine enough to paint the glow-in-the-dark numbers onto the watch faces.

The women employed in this work weren’t just exposed to radiation on the job. Win the “most watches painted in a month” prize and American Radium would give you a bottle of Radithor, a radium-based patent medicine.

Bess frets over the “aftertaste” and doesn’t indulge in glow-in-the-dark makeup parties with her colleagues.

“Stop being a worrywart,” everybody says.

And then one sister gets sick, and she’s not the first. Getting straight answers out of “the company doctor” (Neil Huff) is impossible. It isn’t until the communist photographer (Collin Kelly Sordelet) Bess has taken a shine to suggests that they visit this crusading outfit called The Consumer’s League that they get their first dose of The Truth.

Doctors working for companies like this diagnose “syphilis” to shame the victim and the family into not talking about what’s made them sick. They’ve been hearing from other girls and women. What they need is proof, a corpse that shows that the cause of death might be something nobody knew about at the time, radiation poisoning.

“Radium Girls” uses a carnival barker pitching “radium water,” the “miracle elixir of the age,” and lots of advertising for “radium” products, as well as silent, black and white documentary film footage to lend authenticity to their fictionalized version of this banner moment in U.S. labor history.

A conceit of the film is introducing a sympathetic African American documentary filmmaker (Susan Heyward) character, having her talk about “The Tulsa Massacre,” and the government’s involvement in it, and showing the value of alliances in effecting change.

Not enough is done with that, and the fictional trial, while moving and hopeful, tends to draw matters out.

But Quinn and King carry the emotional weight of the film, and they’re good enough to make “Radium Girls” worth remembering and checking out. They put a moving human face on a story that’s been told in PBS documentaries and books, which gave us the facts, but not the heart of the heroines or the dead souls of the fat cat villains.

MPAA Rating: unrated

Cast: Joey King, Abby Quinn, Cara Seymour, Scott Shepherd, Susan Heyward, Neil Huff and Collin Kelly-Sordelet

Credits: Directed by Lydia Dean Pilcher, Ginny Mohler, Script by Ginny Mohler and Brittany Shaw. A Juno release.

Running time: 1:42