'Tenet': The Movie's Time Travelling Ending, Explained

Tenet is Christopher Nolan's most complicated movie so far, with its constant talk of grandfather paradoxes, reverse entropy, and algorithms. However, the movie saves its most mind-bending twist for the end, when the whole movie is revealed to be a big-time loop. Though this final twist seems complicated when you have been bombarded with physics speak for two and a half hours, it is nothing that has not been seen before in more accessible time travel content like Doctor Who once it is explained.

WARNING: The following contains spoilers for the entirety of Tenet

Throughout the movie, "The Protagonist" (played by John David Washington) does not know much about Tenet, a shady organization that he starts working for to try and stop the end of the world.

He becomes increasingly frustrated about people not telling him anything about the people he is working for, especially as Neil (Robert Pattinson) clearly knows more than him but repeatedly refuses to tell him anything.

At the end of the film, however, it is revealed exactly why no one will tell him anything about the Tenet organization—because it was founded by The Protagonist himself.

After preventing the Algorithm from bringing on the end of the world, The Protagonist takes what he learned from doing so and goes back in time so that he can create the organization that will eventually hire him to stop Andrei Sator (Kenneth Branagh)—essentially, The Protagonist has turned his own life into what Ives (Aaron Taylor-Johnson) would call a "temporal pincer movement."

tenet ending explained
The ending of 'Tenet' reveals that The Protagonist (right) is the one who hired Neil (left) Warner Bros

If that if still too complicated for you, it is basically the same idea explored in the Doctor Who episode "Blink" and the third act of Bill and Ted's Excellent Adventure, both of which are more willing to explain exactly what is going on to viewers.

At the end of Tenet, we also learn exactly why Neil has been so reticent to explain anything to The Protagonist ("P") is that it is a future version of P that hires Neil and tells him everything. In fact, when P goes back in time to hire Neil, the pair become great friends, spending time together that is in Neil's past but is still to come in P's future.

This is why he will not tell him anything—though characters repeatedly say "what's done is done" in the movie, they are worried that if P knows that he is the one who will go ahead and find Tenet, this may change his actions, which may mean that he never goes on to found the organization.

At the end, it is also revealed Neil has been integral to preventing the end of the world in ways that P never even realized. The finale shows that Neil has a red string on his bag, which we have seen at least twice so far in Tenet.

The man who saves P in the Ukraine opera house at the start of the movie had this string on their bag, as did the person moving backward in time who died letting P through the locked room containing the Algorithm.

What this means is, at some point, P goes back in time to hire Neil, and tells him he was saved twice by a man with a red string on his bag. This causes Neil to presumably buy this string (so that P notices he was saved by the same person twice and is able to work out his future connection to Neil) and becomes the man who saves him.

This also means that we know exactly when Neil will die—moving backward in time in the abandoned Russian town, where he lets P into the room and prevents the Algorithm from setting off the apocalypse. This adds another confusing element to the timeline—while most of P and Neil's interactions are in P's future and Neil's past, Neil's death is in P's past (as seen in Tenet) but at some point in Neil's future.

If that is not enough to be getting your head around, Christopher Nolan has one more scene to bewilder viewers. Towards the end, P gives Kat (Elizabeth Debicki) a phone, telling her to call him whenever her life is in danger.

Right at the end, we learn exactly what this was for. P knew that Priya (Dimple Kapadia) would try and kill Kat to keep the Algorithm and the ability to move backward in time secret, so he got Kat to call him telling him the exact moment that Priya turns up to kill him. This means that P can then head back in time and find and kill Priya just before she kills Kat.

Tenet is in cinemas across the world now, and comes to U.S. theaters on September 3.