Say what you will about the time-bending, stop-a-murder-before-it-happens poppycock of “Don’t Let Go,” the damned contraption holds your attention.

Well-cast, but built on the hoariest movie murder mystery conventions, confusingly, inconsistently-plotted yet engrossing and almost moving, it reminded me of John Cho’s missing-daughter mystery of last year — “Searching.”

Because even though this one has a supernatural element, even though the “missing” person is, in fact, merely a few days in the past and perfectly reachable by cell (“Can you hear me now?”), and is a niece, not a daughter, “Don’t Let Go” has the same narrative drive and urgency and pushes a lot of the same emotional buttons.

It’s more of a “good bad  movie,” but dumped on the last weekend of August, I’ll take it.

David Oyelowo of “Selma” stars at “oh so honest Jack Radcliffe, an LAPD detective who is tight with his young teenage niece, Ashley (Storm Reid of “A Wrinkle in Time”). As his brother, her dad, isn’t the most dependable, Jack has given Ashley a cell phone and his number.

So she calls and asks for rides, calls to complain about her dad and calls just to do what teenage girls do with phones — prattle on and on.

Writer-director Jacob Estes (“Mean Creek”) establishes their relation in five brisk opening minutes. And then Jack gets a call with what sounds like panic in Ashley’s static-hidden voice. That leads him to their house, and that’s when he finds the bodies.

Jack barely has time to consider how much time to take off to grieve when his phone rings again, days later. Caller ID? “Ashley.” He refuses to answer, and when he calls the number back, he gets that “disconnected or no longer in service” message.

And then she calls again. Jack answers, and registers the only shock the script will allow him to over this unlikely turn of events.

They talk, cover the same ground they did on an earlier conversation. Jack starts testing hypotheses and quizzing Ashley. She might have information that could lead him to their killers. She might be speaking to him from an earlier period in time.

And a quick glance at a calendar tells him he might be able to “save her” this time. But he’s got to keep this cell connection from his old buddy on the force (Mykelti Williamson of “Forrest Gump”), and from his chief (Alfred Molina of every movie made since “Raiders of the Lost Ark”).

And he’s got to keep Ashley in the dark, too, for reasons less clear. Eventually, as he gives her assignments, we start to see things from her point of view as well as his. She’s digging where he tells her to look, he’s looking where she suggests he dig.

The “You’ve just got to go with this” moments in “Don’t Let Go” are many, some of which may convince you “Nope, not happening.”

For me, a tipping point was a test — chew some gum at their favorite diner, leave it under the table.

“This chewed up piece of gum,” he pleads, “you can un-CHEW it!”

Great actors commit, even if the script tempts them to roll their eyes so’s we know they realize it’s a goof, as we’re certain to catch on ourselves. Oleyowo sells this thing.

Drive-shootings that he barely survives, bleeding out in the evidence room where his colleagues let him statgger, figuring things out he could not possibly know (but not figuring out the killer, which standard Thriller LEGO construction ordains, right in the first act) — it’s all a tad much.

But it’s as much fun as a dumb time-travel murder mystery/cop thriller has any right to be. Just don’t let it keep you up at night sorting through it all, again, the way the folks who take notes (critics) have to. It’ll spoil it.

MPAA Rating: R for violence, bloody images, and language

Cast: David Oyelowo, Storm Reid, Mykelti Williamson, Alfred Molina

Credits: Written and Jacob Estes. A BH Tilt/OTL release.

Running time: 1:42