Director Leslie Zemeckis tells the strange story of Daisy and Violet Hilton in the luridly titled documentary “Bound By Flesh.” Diminutive conjoined twins the Hilton Sisters — stars of vaudeville, occasional movies and carnival midways — were a big attraction in the early 20th century.

In “Bound By Flesh,” Zemeckis — the filmmaker wife of director, producer and screenwriter Robert Zemeckis — blends intriguing photos and film of the Hilton Sisters with commentary from experts and those who knew or encountered them. The documentary unreels an extensive account of the women, from their British birth in 1908 to their deaths in 1969 in Charlotte, North Carolina.

Images of the Hiltons apparently being rare, Zemeckis recycles some film and photos through the course of her 91-minute film. That gets reduntant. The movie would have been more compelling had been edited more tightly, down to 70 or even 60 minutes. Documentarians, biographers, etc., tend to grow too fond of their subjects.

But some footage, being so extraordinary, is worth an encore. There’s a short silent clip of the smiling Hiltons in their teens, for instance, as they walk, unavoidably together, on a city sidewalk. They were indeed bound by flesh.

In addition to being joined from birth by “a ribbon of flesh,” the girls suffered the misfortune of being born to an unwed mother who was horrified by the sight of them. In the hours after their birth, she prayed they would die.

But the sisters lived. Their mother’s employer, proprietor of a Brighton pub, saw a business opportunity. She bought the girls with the intention of placing them on public display.

And so the pattern of the Hiltons’ lives was set. Exploitation followed them throughout their lives. In the beginning, their owner, so to speak, Mary Hilton, was a cold, controlling woman. She forced the girls to take music and dance lessons so they’d be a more bankable stage attraction.

Traveling from England to Australia to San Francisco, the Hilton Sisters proved a goldmine. Meanwhile, their handlers kept them isolated. The girls received none of the huge income they generated.

“They were simply used,” an expert says.

“We signed contracts that were never read to us,” one sister says.

Once the Hiltons were emancipated from those who had essentially enslaved them, they apparently made many bad choices.

The sisters’ film appearances included “Freaks,” directed by Todd Browning, who’d helmed the Bela Lugosi-starring hit “Dracula.” “Freaks” is a classic now but American audiences rejected it in 1932. It was banned in the U.K.

Even as the Hiltons’ careers dimmed and their incomes plunged, they continued working as best they could.

“Bound By Flesh,” in its odd way, is a story of survival. But it’s not a movie that can have a happy ending. Hats off to Zemeckis, though, for shaping the sisters’ not as sad you might assume, sometimes amusing story into a film that’s fascinating like a slow-motion car wreck.

‘Bound by Flesh’

CRITIC’S RATING: Three stars

STARRING: Daisy and Violet Hilton

DIRECTOR: Leslie Zemeckis

NOW SHOWING: Chalmette Movies

RUNNING TIME: 1 hr., 31 min.

MPAA RATING: Not rated.

Excellent (4 stars), Good (3 stars, Fair (2 stars), Poor (1 star)