Christopher Nolan's Tenet doesn't fit the mold of a time travel film. Per established cinematic time travel convention, someone usually moves from one point in time to another. Think Marty McFly using Doc Brown's plutonium-powered DeLorean to go back in time to 1955. Tenet features time inversion, where people and objects move backward along a fixed timeline. There are no multiple timelines here like in Marvel's Loki series. Time inversion is sort of like hitting the rewind button on a remote. Nolan is a bit hazy on the science behind all of this, but maybe radiation is involved? The film acknowledges the challenges of explaining how all this is possible when a character plainly states, "Don't try to understand, feel it."
Moving on to the plot of Tenet, which involves preventing the end of the world. Apparently, the future isn't happy with the way we have abused the planet. Or maybe because we made Stevie Wonder's "I Just Called to Say I Love You" a number one hit for three weeks in 1984. The film kicks off with a classic Nolan action sequence involving a terror attack at the Kiev Opera. We're quickly introduced to the Protagonist, played by John David Washington, a CIA agent working to stop the terrorists (helpfully referred to as the "Protagonist"). It's during a gun battle that the Protagonist notices something unexplainable -- a bullet appearing to travel backward. Things go sideways, and the Protagonist is captured, but then it gets even stranger when his suicide pill is actually a CIA test of his loyalty.
The Protagonist comes to learn of a program called Tenet and is taken to an offshore windmill to wait for his future self to do stuff. Perhaps not surprisingly, it's bad for your future and present self to interact. Considering the backward traveling bullet in Kiev, the Protagonist tracks down the arms dealer in India who sold it to a wealthy Russian named Andrei Sator, played by Kenneth Branagh. To get to Sator, the Protagonist targets the wife Katherine, played by Elizabeth Debicki, who is being blackmailed by Sator after she sold a fake painting to him. The Protagonist agrees to steal the fake from a high-security storage facility in Oslo but finds the painting is not there. Sator knew he was coming.
The film shifts gears, and the Protagonist travels to Italy to befriend Sator, which he does and agrees to help him steal some plutonium in Estonia. Doc Brown had an easier time stealing his off the Libyans in Back to the future. The Protagonist, along with Neil, played by Robert Pattinson, jack what they think is the plutonium after a long car chase, but then a backward driving Sator shows up and demands it. There is a car crash, and the Protagonist is captured by Sator. Detained in a warehouse, we are introduced to the "Temporal Turnstile" concept, a revolving door of sorts that allows people to move backward in time. It turns out the plutonium was not in the briefcase, leading Sator to shoot Katherine and demand to know where the Protagonist stashed it. Buying the Protagonist's lie, Sator heads into the turnstile just as a bunch of good guy soldiers from the future arrive on the scene.
Here's the weird thing about moving backward in time. Because your lungs are reversed, you can't breathe air while inverted, requiring an oxygen mask. Both the inverted Sator and the Protagonist battle it out for the plutonium, but the Protagonist ends up trapped in a burning car. Except because he is inverted, the Protagonist gets hypothermia instead of being burned to death. Flash forward, and the Protagonist, along with Neil and Katherine, are in a cargo ship heading backward in time again, to when he was in Olso trying to steal the forged painting from the secure storage facility. A turnstile at that location allows the three to go forward in time and save Katherine's life. It turns out the plutonium Sator stole was something else, part of a device that, if assembled, inverts the whole planet and spells game over for humanity. This leads us to the last chapter of the film, which involves the Protagonist and Neil stopping Sator's henchmen from exploding the device in Siberia and Katherine killing Sator aboard a yacht in Vietnam.
During the final action sequence in Siberia, we get a close look at the custom watch Hamilton provided the filmmakers. It was based on the Khaki Navy BelowZero but featured an LED digital display on the traditional analog dial. Those wearing watches with red LED displays are traveling forward in time. Those with blue LED displays are going backward. This is an essential detail in the final action sequence where the good guys perform a temporal pincer movement where half the team moves forward in time, jot down notes, and then provides those to the other half traveling backward in time.
In the end, global annihilation is avoided, timeline loose ends are attended to, and the Protagonist learns he recruited Neil in the future. While Tenet may not have a lot in common with time travel genre films, it's a lot like Nolan's previous work in the sense that it's preoccupied with our perception of time. Memento and Interstellar covered similar territory. Is Tenet a great film? It is often hard to follow & probably not suitable for casual viewing. It's an entirely unique piece of filmmaking that challenges the viewer at every turn.
Screengrabs courtesy, Warner Bros.