Back in June, Nolan told Entertainment Weekly that Tenet was not a film about time travel. "This film is not a time-travel film. It deals with time and the different ways in which time can function. Not to get into a physics lesson, but inversion is this idea of material that has had its entropy inverted, so it’s running backwards through time, relative to us," he said.

Therein lies the film's premise: our hero, named The Protagonist (John David Washington), is recruited into Tenet, a secretive spy organization focused on saving the world from a very imminent threat. And while The Protagonist doesn't exactly time travel, he moves through time in a way that's not so far off.

According to Vulture, "The Protagonist is going backward through time... Throughout the movie, some characters are working toward the climax of the movie, whereas others are working backward to it. How? Well, in part, there are events called 'temporal pincer moments' and machines called 'time stiles' that allow characters to invert themselves (i.e. travel back in time)."

In Tenet, The Protagonist must work to stop a "threat that's worse than World War III." Their target is a man named Sator (Kenneth Branagh), who serves as a go-between for people in the future who want to send items back in time that could threaten people, places, or even existence itself.

But according to Wikipedia, Sator actually travels back in time to collect "artifacts [that] are parts of a future-developed "Algorithm" capable of catastrophically inverting the entire world and that future humans are using Sator to activate it in order to prevent the effects of global warming." Wikipedia also reports that, "Sator is dying from inoperable pancreatic cancer [and] he will trigger the Algorithm through suicide via a dead man's switch, believing the world should die with him."

The Protagonist isn't going about all of this alone, either. He's joined by a man named Neil (Robert Pattinson), who not only recruits him into the Tenet organization, but joins him as a partner on his mission. "Once I realized that you can play Neil as someone who enjoys the chaotic situation he's in, then that seemed to be the touchstone for the rest of the character," Pattinson told Digital Spy. "When you see the Protagonist try to deal with this new situation that's incredibly difficult to deal with, it's not pleasurable for any of the characters... and Neil is just one of those people who's like, 'Oh, I love this, I love living in a nightmare.'"

Also joining the Protagonist is Kat (Elizabeth Debicki), art dealer and wife to Sator, as well as an asset for the Protagonist in his mission to get close to Sator and find out his initial plans. According to Vulture, she confesses to the Protagonist later on that she wants to be free of Sator, and that she has recurring dreams of seeing a woman leaping from a yacht into the water to swim away to safety — a small, but important detail that reveals its importance later on.

Eventually, the Protagonist, Neil, and another mysterious special forces character, Ives (Aaron Taylor-Johnson), band together to stop Sator's plan, stealing one of the "artifacts" he was going to use to cause the end of the world. (The terminally ill Sator had set things up so that the moment his heart stops beating, they would all trigger across time and reverse the universe's entropy, according to Digital Spy.)

While the trio work to retrieve the device, Kat is working to distract Sator from killing himself on his yacht — which, again, would trigger all the devices and result in an end-of-the-universe scenario.

The Protagonist and Ives successfully secure the device, but not without cost: Neil is killed in the process, but for his sacrifice, they manage to foil Sator's plan. Kat, unaware of the mission's success, kills Sator herself, and dives from the yacht into the water below. As it turns out, the woman from her dreams swimming to freedom was actually her.

Towards the end of the film, Neil's secret comes to light. According to Wikipedia , "[before he dies] Neil reveals that a future version of the Protagonist recruited him to Tenet years earlier, and this mission is the end of a long friendship that the Protagonist has yet to experience. In London, Priya attempts to kill Kat but is killed by the Protagonist, who is the future mastermind behind Tenet."