This Nazi zombie romp sounds glorious on paper, but it's a drag waiting for the dead to start twitching.

There’s nothing wrong with making genre fans wait for the good stuff.

“The Descent” told a cave exploring yarn long before the sightless monsters entered the frame. It was more than worth the wait.

“Overlord” takes forever and a day before revealing its grindhouse surprises. When they arrive, they’re only perfunctory at best.

Yes, that’s a problem.

The story follows a group of American paratroopers entering Nazi-occupied France during World War II. They’re tasked with taking down a critical radio tower to prepare Allied troops for the D-Day invasion.

They team with a French villager (Mathilde Ollivier) and her adorable son to avoid German troops and make their way to the tower. Only they discover a creepy lab where Nazi experiments turn the locals into … something sinister.

Fair warning: This is not your standard Nazi zombie affair. That’s both refreshing and a bummer. “Dead Show: Red Vs. Dead,” a conventional zombie romp, remains a genre delight. Who wouldn’t mind a spiritual sequel?

Jovan Adepo (“Fences”), Wyatt Russell (Son of Kurt) and John Magaro lead a talented cast of heroes brimming with war-time stereotypes. Adepo is the new kid on the war front, while Magaro can’t stop cracking wise. All are forgivable given the film’s genre trappings.

“Overlord” overstays its welcome in more ways than one. It pretends we’re wholly invested in characters when that’s hardly the case. The details behind the group’s mission aren’t intriguing enough to warrant so much attention.

And a 109 minute running time? Unforgivable given the story’s slack pacing and modest ambitions.

FAST FACT: “Overlord” director Julius Avery is tasked with bringing “Flash Gordon” back to the big screen.

When the dead start to rise we’re treated to a few nasty surprises. This isn’t the grunt and slump school of zombies. We won’t say how they act, but just know it’s one of the film’s freshest riffs.

Even better?

The Nazi officer we fear the most (Pilou Asbæk) is a mustache twirler of the first order, and all the better for it. Director Julius Avery (“Son of a Gun”) delivers a few meaty jolts, more than you expect given the lackluster presentation.

Otherwise, we’ve seen the grindhouse third-act before. Without more surprises, “Overlord” is a genre smashup with little to recommend it at full marquee price.

HiT or Miss: “Overlord” fuses zombie tropes with wartime cliches, but what emerges is neither fresh nor invigorating.