Sandra Bullock anchors a sporadically gripping tale of a world where opening your eyes can be deadly.

What’s Sandra Bullock doing in a Netflix genre film?

The Netflix part is easy. Everyone is lining up to work for the streaming giant. Even Martin Scorsese joined the Netflix revolution via the upcoming mob movie “The Irishman.”

The genre question? That’s stickier, especially since Bullock’s “Bird Box” veers from thoughtful sci-fi to silly grindhouse fare.

There’s nothing wrong with either approach. Mixing the two can be calamitous. Thankfully, the elegant storytelling scores a KO, but not before the film’s goofy side lands a haymaker or three.

Bullock’s Mallory is expecting her first child, but she’s hardly excited about the prospect. That ambivalence gets shoved aside when the end of the world breaks out.

Really.

People start taking their own lives in garish fashion. It happens all at once, and Mallory scrambles for shelter inside a nearby home. There she meets a gaggle of dystopian characters types including the pragmatic jerk (John Malkovich), the hunky do-gooder (Travante Rhodes) and the comic relief (Lil Rey Howery, “Get Out“).

The survivors quickly suss out the problem. Anyone who opens their eyes outside is susceptible to a force turning people into suicide machines. That revelation is one of many head scratchers we’re asked to accept along the way.

Gulp hard and go with it.

We learn a bit more about the existential threat, but once again the revelations hardly make sense. Science fiction offers lots of logical wiggle room. .That pliability is sorely tested here.

That leaves us with Bullock, giving it all the gravitas in her tool kit. She drills into Mallory, never phoning in so much as a glance. The screenplay helps and hurts her cause. There’s a palpable theme of motherhood that enriches the thrills. Her wariness may depend on the situation, a fascinating subtext.

There’s also a sense of been, there, been scared half to death by that throughout the film. No, this isn’t a zombie move, but some of the genre’s storytelling tics replicate themselves here. “Bird Box” manages to bring some novel twists, though.

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The blindfold strategy mirrors the constant “shushing” from “A Quiet Place,” and it’s equally effective. Our heroes must be both brave and clever to survive, and watching them attempt both offers a satisfying rush.

Even better?

Mallory isn’t a soulful Survivor Girl type. She’s crusty, but not in any forced way. You wouldn’t want to cross her, but you also might cross the street to avoid her.

“Bird Box’s” narrative risk saps some, not all, of the tension. The story shows the start of the suicidal outbreak in chronological order. It’s interspliced with scenes of Mallory and two young children embarking on a dangerous river trip.

You don’t need a crystal ball to spot who’s missing on her small boat.

Director Susanne Bier keeps things moving, but she succumbs to some old slasher movie gimmicks along the way. Case in point: one character suffers a mortal wound, and the camera lingers on the blood pooling around his head.

Did Rob Zombie drop in on the set and grab the camera from Bier?

Just. Not. Necessary.

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And did we really need a main character trot out a variation on President Trump’s “Make America Great Again” slogan? The line comes out of nowhere and stops the movie cold.

Those clanging elements fade in the third act, and we’re left with a satisfying survival yarn with a complex hero. Ultimately, that renders “Bird Box” a flawed but worthy addition to the dystopian film wave.

HiT or Miss: “Bird Box” veers from sober sci-fi to genre clock punching, but a committed Sandra Bullock makes it worth your while.