Earlier this year “Wonder Woman” became a critical hit and box-office smash — it’s made more than $412 million and finally gave us a woman as a butt-kicking superhero.

Now comes “Professor Marston and the Wonder Women,” a movie with a far more interesting story about how the inspiration for Wonder Woman comes from the world of bondage, S&M and sexual freedom — and it’s true.

It’s not as good a movie, though.

It’s not a bad one, either. Writer-director Angela Robinson’s film doesn’t explore the comic-book origins of the superhero as much as it does the real-life man who created her, and he was a fascinating guy.

Robinson uses a framing device, beginning with William Moulton Marston (Luke Evans) being interrogated by a religious-based family-values group (led by the great Connie Britton, who sadly doesn’t have much to do).

Why, the group wants to know, do so many Wonder Woman comics — practically all of the early ones — involve women tying men up, or vice versa, or each other? There’s spanking, there’s women wresting women. What’s going on here?

Therein lies the real tale.

In repeated flashbacks we see William, a Harvard professor, teaching a graduate course to women in 1928, explaining his DISC theory of human behavior: dominance, inducement, submission and compliance. Watching is his wife, Elizabeth (Rebecca Hall), the smarter of the two, but Harvard’s sexist policies are preventing her from receiving her doctorate. She too is on the staff, and they work together. One of their projects includes advancements in the lie-detector machine.

They’re progressive in their views, and William in particular promotes feminism often (sometimes a bit too often, to the detriment of Robinson’s script). William notices a student, Olive Byrne (Bella Heathcote) and, clearly attracted to her, begins flirting with her and hires her on as an assistant. Elizabeth has always in theory advocated an open marriage (“I’m your wife, not your jailer”), but when push comes to shove, the first time she meets Olive she asks her one favor: Don’t sleep with my husband. (She uses earthier language.)

Olive is horrified and wants to quit, but William and Elizabeth take her out to a speakeasy, where they learn that Olive’s mother is Ethel Byrne, a radical feminist, and her aunt is Margaret Sanger, who would found Planned Parenthood. They’re suitably impressed, and Olive stays on.

On the newfangled lie detector, the truth comes out: They are attracted to each other, want to have sex with each other, love each other.

So begins a polyamorous relationship. (It actually begins in the costume room of a college theater, with dress-up games and the most-tasteful threesome you’ll ever see — tasteful in that with all the outfits and gauzy lenses you can’t tell what’s going on.)

They don’t do much to hide their new arrangement, and scandal follows. William and Elizabeth are fired, but the three set up a home together. William would father two children with each woman; if neighbors got nosy, Olive was a widowed sister taken in by the Marstons. William is unhirable. Elizabeth, a string of graduate degrees trailing behind her, finds work as a secretary. Olive stays home and takes care of the kids.

One day William wanders into a New York shop, looking for lingerie. He finds it, as well as S&M gear the proprietor sells in the back — along with a show to model his wares. He brings Elizabeth and Olive in for a show, and Olive winds up in large bracelets, a corset and a tiara, with a rope — used for bondage — looped and hanging from her waist.

Sound familiar? Superman wasn’t born this way.

Inspired, William comes up with a character, which will become Wonder Woman. The comic is a huge hit — until it trips the wire of conservative do-gooders. William offers a simple defense: Wonder Woman is a strong woman dominating a man’s world — the culmination of his academic work playing out in comic-book panels. Plus, sexuality is healthy.

Imagine how well that went over.

Robinson tells the story in a straightforward way, not quite breezy but definitely in mainstream fashion. You long for a little more grit, even the rough edges seem a little smooth.

But the cast is good (Hall, always terrific, is the best thing about the film), and the story is undeniably compelling, making “Professor Marston and the Wonder Women” a nice companion piece to one of the biggest movies of the year, and a good movie in its own right.

Bill Goodykoontz, USA TODAY Network

★★★

Annapurna Pictures presents a film written and directed by Angela Robinson. Rated R (for strong sexual content including brief graphic images, and language). Running time: 108 minutes. Opens Friday at local theaters.