One of the many things broken by the COVID pandemic was the covenant between horror movie makers and their audience.

Horror movies just aren’t the same on a small screen once you’ve cleared your tweens. They demand to be seen in a theater with an audience of the like-minded, ready to revel in our communal fright — or derision if the frights aren’t there.

It’s a simple matter of screen size. A big screen sucks you in, overwhelms you. No matter how big your TV, that just doesn’t achieve the same effect at home. Seeing a thriller in a theater, even a nearly empty one, is more overwhelming.

Size matters.

I’ve spent the year reviewing horror movies without those crowd-sourced scares, and it’s left me at a loss as to whether say, “The Dark and the Wicked” really worked.

Conversely, the theatrical release “Come Play” is a Slender Man horror movie with a few genuinely hair-raising moments and some good effects. Writer-director Jacob Chase times out the jolts well.

But the adults involved can’t decide if they’re stunned by their (presumably) first encounter with the supernatural, or if they’ve seen so many horror movies that they just accept this digital (electrical) threat to their child at face value.

The most promising idea, a rigid adherence to experiencing something through the eyes and ears of a speechless autistic boy, is fudged here and there — the “scare him out of it” cinematic cure. And the ending is a cop-out.

Still, that’s a great hook. Lonely little Oliver (Azhy Robertson) communicates via a type-to-speech phone app, and is teased at school over it. He’s sensitive to noise, and damned if his condition isn’t driving his parents (Gillian Jacobs, John Gallagher Jr.) apart.

That’s the perfect time for the eBook “Misunderstood Monsters” to viral its way onto his phone. He switches off “Sponge Bob” long enough to swipe a few pages. He starts hearing noises, thumps and footsteps. Lights pop and flicker out. A clever boy, he turns the phone camera-and-light on, and that’s where he sees “Larry.” The book says Larry just wants a friend.

We know better.

Robertson, the kid from “Marriage Story,” whimpers and quakes at what he’s seeing. Mom isn’t much comfort. Dad’s keeping a roof over their heads with multiple jobs, including one as a night watchman/clerk at a pay parking lot. He’s distracted.

Eventually, after the kids who bully Oliver have a sleepover that turns horrific, even his parents catch on. This cadaverous, skinny thing is coming for Oliver.

Writer-director Chase, expanding his short film “Larry,” cleverly gives us Larry’s-eye-view shots of the monster looking through (sometimes busted) cell phone and iPad screens.

I was impressed, for a while, with how closely he adheres to the limitations of autism, and the ways it doesn’t signify low intelligence. Some of Oliver’s clever reasoning his way out of tight spots or how to “explain” what’s going on is beyond-his-years (about 8), but for the most part, there’s not much here a non-expert would quibble with.

The film’s theme is hammered and hammered hard — digital devices make even the non-autistic lonely and cut-off from the world (And autistic kids are really into screens, we’ve heard.), so Larry has fertile hunting grounds for “friends.”

Chase wimps out on his whole “bullying” subtext (Winslow Fegley is effectively childish and cruel) and losing the conceit of the kid having to fight this threat on his own is a major blunder.

As impressive as Jacobs’ (“I Used to Go Here,” TV’s “Love”) “fear face” can be, she’s maddeningly inconsistent in her reactions to the menace she and her little boy face together.

One of the stresses on the marriage is their child’s disconnect from each parent, not even making eye contact with his own mother. Even taking that into account, there’s little “mothering” or “fathering” about the relationships.

Gallagher (TV’s “Westworld”) at least manages a proper freak out or two.

The best effect is the wind blowing pieces of paper across the parking lot as husband-dad Marty fiddles with the light in his glassed-in booth, totally unaware that the paper is wrapping itself around the hidden monster in the dimly-lit space behind him.

So yes, there’s good stuff here, mostly in the earlier acts. But even mixed-bag horror flicks like this can work if they’re seen on the big screen. When this virus is finally beaten back, filmmakers and fans have a covenant to renew., fffi

MPA Rating: PG-13 for terror, frightening images and some language

Cast: Azhy Robertson, Gillian Jacobs, John Gallagher Jr. and Winslow Fegley

Credits: Written and directed by Jacob Chase. A Focus Features release.

Running time: 1:37