“Disappearance at Clifton Hill” is an indie murder mystery set in one of North America’s most infamous tourist traps — Niagara Falls.

It’s got a winning cast. Tuppence Middleton of “Downton Abbey” and “The Current War” is our troubled heroine. Iconic Canadian director David Cronenberg plays a local conspiracy crank who may not be a “crank,” and who has his own podcast.

Who WOULDN’T listen to a Cronenberg (“Scanners,” “A History of Violence”) podcast on Niagara Falls conspiracies?

But the movie, taking its name from the Canadian tourist strip Clifton Hill, is a clumsily over-complicated affair with the odd moment of suspense, a lot of local color and a plot that utterly outsmarts itself by the end.

Abby was only seven years old, fishing with her family, when she saw him — “the one-eyed boy.”

He was hiding from someone. When a Chevy Impala parked just up the hill, he fled, but in vain. Two adults grabbed him, beat him and shoved him into the car.

Abby was too frightened to say anything. She finally told her sister, Laure. And Laure, just as little, never believed her.

Twenty-five years later, memories of this long-ago trauma, which may have triggered a lifetime of lies, deceits and off-the-beam behavior, comes back to Abby (Middleton) as she returns to Niagara Falls to settle her mother’s estate.

She and Laure (Hannah Gross of “Joker” and “Mindhunter”) are to sell the old Rainbow Inn, the family motel on the Canadian side of the falls. The family that controls most of the tourist trappy kitsch attractions wants the land.

“The haunted houses aren’t actually haunted,” Abby jokes to a barfly she’s flirting with. “The funhouses aren’t actually fun.”

But Abby is reluctant to close this door, puts off the entreaties of Charles “Charlie” Lake III (Eric Johnson), heir to that funhouse/wax-museum/arcade empire that wants the Rainbow. When she rummages through her late mother’s photos, she remembers why.

Who WAS that “one-eyed boy?” Her first clue that she didn’t just dream it all up is there on film.

Her sister rolls her eyes, and the new cop in town Abby picked up in that bar (Andy McQueen) is dismissive in a most-un-Canadian way. But the diver she stumbles into, down stream from the falls, takes her seriously.

Walter Bell (Cronenberg) is a longtime member of the volunteer corps that hunts for bodies after they’ve jumped or fallen over Rainbow Falls.

“Do you know what happens when a body hits the bottom of the gorge?” Cronenberg’s eyes glaze over a little as he asks the question, as if he’s about to salivate over the idea of showing what “swallowing a grenade” looks like in a movie of his own making.

Walter has theories about the long-missing kid and passes on rumors via podcast that should get him sued. Abby listens and does her own digging through photos, old promotional videos and archived newspaper stories in the library.

We can do the math. She’s unsettled, no career and in her ’30s. She doesn’t have to tell us she studied journalism in college. “Crazy” is something her sister hints at, but girlfriend knows how to hunt down facts and leap to conclusions about them.

Director and co-writer Albert Shin (the Korean drama “In Her Place” was his first feature) gives “Clifton Hill” a vivid, immersive sense of place. There’s a diner themed as a flying saucer, casinos, seedy “funhouses” so old that Robert Ripley could have visited them (“Believe it, or Not!”) and a few “off season” tourists (It hasn’t snowed — yet.).

But the story stumbles along, never quite selling the worn-out “This might be all in Abby’s head” conceit, never quite playing fair, never making enough sense to allow us to reason out a solution or accept the coda that Shin & Co. slap on it.

The effect is a muted thriller that delivers a couple of good scenes, and one electric one — a late-night diner confrontation featuring an accented local magician/lion tamer played by Marie-Josée Croze.

That adds up to a muddled mystery-thriller that’s something of a wash, one that director-turned-actor David Cronenberg all but steals. And that “Over the Falls” podcast his character hosts? I’d pay to hear that.

MPAA Rating: unrated, violence, adult themes and situations

Cast: Tuppence Middleton, Hannah Gross, David Cronenberg, Eric Johnson and Marie-Josée Croze.

Credits: Directed by Albert Shin, script by James Schultz, Albert Shin. An IFC Midnight release.

Running time: 1:40