TENET: Fasten your seatbelt

* * * (out of four)

After seeing “Tenet,” I suspect maybe writer-director Christopher Nolan was irritated that so many viewers guessed the ending of his 2014 hit, “Interstellar.”

In any case, this exciting new film is so insanely fast and complex, I doubt one viewer in 100 could follow the entire thing.

What’s remarkable is that despite its brain-bending, pell-mell plot, the film remains consistently thrilling; one never detaches or gives up on the story, even though a little voice keeps asking, “What the #$%@ is going on now?!”

As he’s shown in such gems as “Memento,” “The Prestige” and “Inception,” Nolan is a good enough storyteller that one can always track the general contours of his plot, even if the details are rather confusing.

Here, that convoluted narrative involves the titular organization of secret agents, which is working to prevent some sort of unprecedented global catastrophe. While initially this bills itself as World War III, the threat is actually worse -- and it hinges on “inversion,” a process from the future by which time can be reversed so that bullets fly backwards and fallen people rise. And then on top of that: Despite the movie’s sprawling length, “Tenet” moves at 100 miles an hour, with plot points hurtling past so fast that you may find yourself in a running discussion with seatmate(s) trying to make sense of it all.

By far the most head-hurting aspect occurs in several scenes where some characters are inverted and others aren’t. Just imagine a fist-fight -- or worse yet, a car chase -- with some people moving forward in time and others moving backward. Watching these sequences feels like running across a floor made of golf balls; yet somehow, the action scenes are thoroughly enthralling despite the constant confustication.

Much of this is due to first-rate editing by Jennifer Lame, stepping in for Nolan’s usual cutter, Lee Smith -- who was busy working on “1917.” And then there’s the little matter of the director’s fondness for practical effects, rather than computer-generated visuals. Nowhere is this more apparent -- and successful -- than the spectacular airport scene, in which an actual 747 smashes into a massive building.

Indeed, every penny of the movie’s hefty $200 million budget is visible onscreen; the action scenes are on par with James Cameron or George Miller, and the acting is superb.

That, in fact, is the principal manner in which Nolan holds interest through his intellectually difficult proceedings: Thanks to fine performances from John David Washington, Robert Pattinson and Elizabeth Debicki, we really care about these people and their problems, which frontline selfless love and poignant, intimate family dynamics amid the hurly-burly. Kenneth Branagh makes an extremely impressive villain, giving what I consider the finest performance in this film -- and perhaps in Sir Kenneth’s own distinguished career.

All this helps us overlook the typical logistical problems in time-travel tales, highlighted by the concluding and unsolved puzzle of how there now appear to be two different incarnations of the same character somewhere in the world.

I remain baffled by this aspect of the plot. These enigmas, along with the amazing action scenes, compel me to see it again soon -- though maybe this time, I will need to watch it backwards.

“Tenet,”

directed by Christopher Nolan

Run time: 150 min.

Rated PG-13 for intense action and brief strong language