Wow. Did not see THAT coming.

The German hijacking thriller “Blood Red Sky” hides its hand so well early on that it’d be a shame to give much of that away. The surprises have a grim delight about them, the violence a righteous, maternal fury.

It’s a clever blend of over-the-top supernatural and “work the problem” logical. It’s well-acted, harrowing and violent. And every now and then, this absurd German thriller is more fun than it has any right to be.

The framing device is a hijacking that’s just ended, the transatlantic jetliner, piloted by a passenger, has touched down in Scotland. There are hijackers still on board, but a little boy   (Carl Anton Koch) slips off before the hijackers start negotiating.

And boy, does he have a story to tell. Only he’s not speaking.

A long flashback shows how young Elias boarded the plane with his sickly mother
(Peri Baumeister of “The Last Kingdom”). We’ve seen her don the wig, seen her Skype with a New York doctor. They’re flying from Germany to America for treatment.

The mid-flight assault itself is brutal and coordinated. The hijackers know how to “out” air marshals and aren’t shy about spilling blood. There are “crew members” in on it. There’s a “frame-up” planned.

The leader (Dominic Purcell) is pitiless. But his gang includes at least one psychopath (Alexander Scheer). Let’s call him “Eightball.”

The passengers panic and weep and submit and can’t reason out what the villains’ motive or end game is.

“Our one demand is strictly monetary,” the leader purrs, after the first killings. The passengers have their doubts.

“Everything is fine, sweetie,” Mom assures Elias. He doesn’t believe her. He’s a smart kid trying to form his own escape plan.

And the villains? They haven’t reckoned on sickly Momma Nadja. They haven’t seen her flashback-within-the-flashback. They don’t know she’s been through worse. And now it’s not her trapped in a jetliner with them, it’s a gang of brutes trapped onboard with one fiercely protective Mama.

Director and co-writer Peter Thorwarth, best known for the cautionary parable “The Wave” (a high school exercise in how Nazis take over), and co-writer Stefan Holtz (they did “Not My Day” together) work the genre conventions to contrive their screenplay’s obstacles, and the characters’ solutions to those.

There’s an efficiency that settles in and manifests itself through the problems and the problem solving. The viewer is in on it, because we “get” the genre conventions they’re playing around with, we know why X, Y or Z as a counter-measure will work.

And Baumeister, playing the struggle of maternal instincts vs. more base and horrific impulses, is terrific as Nadja. There is pathos and power, fury and fatalism in this tightly-coiled turn.

Sorry for being so cryptic, but the first big “reveal” here is a winner, and best served cold. Suffice it to say that this is a lot closer to “Snakes on a Plane” or “Into the Night” than “Flightplan” or “Die Hard 2.” Kind of a send-up, but serious as a heart-attack.

If gory genre pics with subtitles (its in German and English with subtitles, or dubbed into English) don’t scare you off, “Blood Red Sky” could be just the ticket.

MPA Rating: TV-MA, graphic violence, profanity

Cast: Peri Baumeister, Carl Anton Koch, Alexander Scheer, Kais Setti, Graham McTavish and Dominic Purcell

Credits: Directed by Peter Thorwarth, script by Stefan Holtz and Peter Horwath.  A Netflix release.

Running time: 2:03