'Tenet' ending explained — a complete breakdown of the finale of Christopher Nolan's new movie

• WARNING: Spoilers for "Tenet" ahead.
• Christopher Nolan's new movie "Tenet" can be hard to get your head around, so Insider has broken down the ending of the film, and explained exactly what happens in the finale.
• "Tenet" follows John David Washington's Protagonist trying to stop Kenneth Branagh's Sator from ending the world via an algorithm that inverts the world's entropy.
• The final sequence sees half of the Tenet strike team traveling backwards in time and half traveling forwards in a bid to find and stop Sator's algorithm.

Christopher Nolan movies are best described as blockbusters with brains. And his latest, the palindromic "Tenet," is no different.

The film follows John David Washington's Protagonist, who is aided by Robert Pattinson's Neil and Elizabeth Debicki's Kat, trying to prevent the end of the world. But the Protagonist's mission takes on a time-travelling twist as he works to put a stop to villain Andrei Sator's (Kenneth Branagh) plan.

A second (or third) viewing will likely help to understand this movie further, but we've broken down the entire ending of "Tenet" and explained what it all means.

What the hell is entropy?

After surviving an assault at an opera house and trying to kill himself rather than give up information to the enemy, the Protagonist is recruited by a mysterious man to embark on the "Tenet" mission and save the world.

He quickly learns of a new type of bullet — ones that have been manufactured so that their entropy is inverted, meaning they travel backward in time rather forward.

To borrow Den of Geek's definition: "Entropy can be described as a measurement of how much information is needed to describe a system."

DoG's Chris Farnell continues: "Because the second law of thermodynamics states that the amount of entropy can only increase, throughout history many scientists and philosophers have used the increase of entropy as a handy by-word for the arrow of time – the idea that everything moves from the past, to the future."

In "Tenet," entropy can be inverted, meaning that less information is needed to measure a system and instead of disorder being the end result, the opposite happens: order. For example, if you were to reverse the entropy of a cheese grater, the grated cheese would go back through the grater and reform into the block of cheese (order), whereas normal entropy would mean the cheese goes from the block, through the grater, and into a grated heap of cheese (disorder).

Think of the line in the trailer where Clémence Poésy's scientist says: "You're not firing the bullet, you're catching it."

It's this manufacturing process, of inverting the entropy of things so they move backwards in time, that is the key to the mission and the movie.

The Protagonist and Neil find out that Sator is the one manufacturing the bullets, and encounter a time turnstile, which allows anyone who goes through it to travel back in time. Sator's overall goal is to find and unite numeral pieces of an algorithm that were split up and hidden in the past that, when combined, will invert the entropy of the entire world, which basically means the world will be destroyed. The algorithm will be activated via Sator's dead man switch. He has a terminal illness and plans on killing himself, which will set off the end of the world.

Explained: The 'temporal pincer movement' at Stalask-12

The final sequence of the film takes place in a delipidated Soviet-era city called Stalask-12, and the Protagonist, Neil, and the Tenet organization (led by Aaron Taylor-Johnson's Ives) undergo a 1o-minute assault of the city in order to find the completed algorithm, which they tracked there.

They do this via a "temporal pincer movement," which means that half of the soldiers (including the Protagonist and Ives) will move forward in time to the blast zone of the city, while the other half will move backwards in time (including Neil).

Meanwhile, Kat heads through a turnstile, inverting herself, and joins her husband Sator on a yacht in Vietnam, which is the place and point in time where Kat and Tenet believe Sator will kill himself to set off the end-of-the-world algorithm.

However, the Protagonist and Ives are prevented from reaching the assembled algorithm, which is buried in the ground and is in the process of being dug up for use by Sator's forces, by a locked gate. However, an inverted dead body becomes alive again and "catches" a bullet, saving the Protagonist from being shot. The body also manages to unlock the gate.

NB: the body's rucksack has a red tag on it. Earlier at the start of the movie, a soldier with the same red tag saved the Protagonist in the opera house.

Back on the yacht, Kat is unable to resist and ends up killing Sator earlier than planned, but does so just as the Protagonist and Ives manage to deactivate the algorithm, putting a stop to Sator's plan.

Kat then jumps off of the yacht to escape, which her past self sees — she had earlier mentioned to the Protagonist that she saw a woman jump off of the yacht on that day and envied her freedom. It turns out her future self was that woman.

Keep a close eye on Robert Pattinson's Neil

With the mission accomplished, the Protagonist, Neil, and Ives agree to split up and hide the components of the algorithm to stop it from being used ever again. But Neil tells the Protagonist that he needs to head back into the event, meaning he will invert himself again, to ensure that the locked gate gets unlocked for the mission to work.

As Neil turns to leave, however, the Protagonist notices that familiar red tag on Neil's rucksack, meaning that it was Neil who saved the Protagonist at the locked gate and also at the opera house. This also means that Neil will die, bringing the end of their friendship, whereas the friendship is only just starting for the Protagonist.

Neil explains that it was actually a future version of the Protagonist who was the one who recruited him to the Tenet mission years ago.

The Protagonist realizes that he is actually the mastermind behind Tenet and is the one who orchestrated the entire events of the film to ensure they stop Sator's plan. In the movie's final scene, the Protagonist stops arms dealer Priya (Dimple Kapadia) from killing Kat, accepting that he is the true person behind Tenet.

Read more:

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