THE BOOGEYMAN

Vivien Lyra Blair stars in ‘The Boogeyman,’ a film shot in New Orleans but set in Anywhere, U.S.A.

It’s a potential problem for anyone making a movie based on a short story: How do you expand the narrative to feature length without making it feel padded — or, worse, like something entirely different and disconnected from its source material?

For the makers of “The Boogeyman,” based on the 1973 Stephen King short of the same name, the solution is elegant in its simplicity.

Rather than try to stretch King’s yarn, they simply use it as a starting point. The events of that original seven-page creepout are covered within the film’s first 20 minutes. Then, director Rob Savage and company imagine what happens next.

And what does happen next?

Generally speaking, audiences can expect a moderately effective, PG-13-rated monster-in-the-closet chiller that plays like a horror movie for people who like the idea of horror movies more than they like actual horror movies.

There are jump scares. There is mounting tension. And of course there is the titular Boogeyman, that nightmare-dwelling, child-devouring monstrosity of which seemingly every culture has a version.

That seems familiar

At the same time, aside from that inspired starting point, it’s missing much imagination or ingenuity. Consequently, Savage’s “Boogeyman,” while atmospheric and earnest, feels vaguely like an episode of “The Twilight Zone” genetically crossed with “Poltergeist.”

That is to say, it has its scares — but it all also feels exceedingly familiar, right up to the obligatory set-up for what the studio clearly hopes will be a sequel.

Most King fans are probably familiar with the short that inspired the film. They’ll also recognize it in the film, as Savage re-creates it with laudable faithfulness at his film’s outset.

Set in the office of a therapist, it begins with an unexpected visit from a clearly troubled patient who is determined to unload his horrifying story. That story centers on an otherworldly creature that lives only in darkness and which was behind the deaths of all three of his children within a single year.

When he’s done, he leaves the office — and King delivers a twist ending that leaves readers realizing he wasn’t quite as crazy as we were led to believe.

THE BOOGEYMAN

Sophie Thatcher, left, and Vivien Lyra Blair are sisters being pursued by a shadowy being with ill intentions in the atmospheric chiller ‘The Boogeyman.’

Just the beginning?

In Savage’s film, that therapist is played by everyman Chris Messina (“Air”), his patient is David Dastmalchian (“Boston Strangler”) — and that twist ending is only the beginning.

In this version, based on a screenplay by Scott Beck and Bryan Woods (“The Quiet Place”) with Mark Heyman (“The Skeleton Twins”), we learn that Messina’s therapist character is struggling with the recent unexpected death of his wife in an auto accident.

Every bit as grief-stricken are his now-motherless young daughters, teenager Sadie (played by Sophie Thatcher, of “Yellowjackets”) and the younger Sawyer (played by 10-year-old firecracker Vivien Lyra Blair, of “Obi-Wan Kenobi”).

For the rest of the film, Sophie and Sawyer find themselves either trying to convince grown-ups there really is something hiding in their bedroom closet, investigating the source of that something or — in the inevitable third-act showdown — fighting for their everloving lives against the film’s insatiable CG baddie.

In addition to boasting an appealing cast, this “Boogeyman” appealingly flips the script in that, rather than being a cautionary tale for children, it becomes a cautionary tale for adults.

A shadowy threat

As Dastmalchian’s character explains, the emaciated Boogeyman at its center — all knees and elbows and a Gollum-like obsession — is “the thing that comes for your kids when you’re not paying attention.”

In this case, it’s intended to be a metaphor for grief, a dark, shadowy thing that can overtake and destroy a family if they let their guard down. Really, though, it can serve as a metaphor for any invasive familial threat.

To some, it might represent the danger social media poses to their children. To others, it might be an ex-spouse. It could be a stand-in for gangs, gambling, drug use or any other real-life boogeyman.

If only the rest of the film were so well-thought-out. Instead, “The Boogeyman” engages in many of the traditional horror tropes to keep things moving, starting with the staggering stupidity of its main characters.

They hear a sound in the darkened basement? They go investigate, the morons. They hear something scuttling under the bed? They flop onto the floor to check it out. They’re being pursued by a malevolent force? They choose not to call for help.

Better than expected

Most frustratingly, they fail to do the one very reasonable action that any rational person would do — and which would end the film before it gets started: Leave. The. Dang. Lights. On.

Even with its flaws, a fair argument can be made that “The Boogeyman” is better than it probably should have been. It certainly exceeded the expectations of 20th Century Studios brass, who scrubbed the film’s planned streaming-only release in favor of a wide theatrical release.

None of that, however, changes the fact that “The Boogeyman” — for all it does right — runs out of inspiration around the time most people will have run out of popcorn.

Mike Scott can be reached at moviegoermike@gmail.com.