Tenet Explained

Who is the hero? 

The hero is a young CIA agent who is never referred to by name. Let's just call him The Protagonist since that is how he identifies himself in the final scene. During the undercover operation at the Kiev opera house at the beginning of the film, he, along with a mysterious masked soldier with a strange looking red trinket, fail to retrieve an artifact. However, the Protagonist witnesses this masked soldier inverting a bullet as if it was travelling backwards. The Protagonist is captured by Russian mercenaries who torture him, but he does not expose his team. Impressed by his loyalty, he is saved and recruited by Tenet.

What is Tenet? 

Tenet is a mysterious organisation that aims to prevent the creation of a machine that could lead to the end of the world. The Protagonist is sent to a scientist named Barbara, who is studying a strange set of weapons with "inverted" entropy, similar to the bullet The Protagonist witnessed in Kiev. This allows them to move backwards through time, such as having the ability to enter The Protagonist's grasp even before he grabs them. Barbara believes they are able to move like this because they were made in the future. The Protagonist traces the materials used to manufacture the weapons to an arms dealer in Mumbai.The Protagonist teams up with another Tenet member, Neil, to confront the dealer. It is then revealed that the dealer's wife, Priya Singh, is a senior member of Tenet. She explains that she sold her weapons to one Andrei Sator, a wealthy Russian oligarch who not only has the ability to invert time, but can communicate with the future. When she sold him the weapons, they were not yet time-inversed. 

The time inversion machine

In the distant future, a scientist has invented a time inversion machine. However, fearing that it will be used for evil, she divides its algorithm into nine components and hides them in the past. She achieves this by time-inverting herself and then re-inverting herself to align with whatever time period she is in over and over again until she manages to hide all nine components in different nuclear locations across the world where the components will be safely hidden away. Unfortunately, in present day, Sator has uncovered all nine components, including the final one which The Protagonist was out to get in Kiev. 

Sator’s evil plan

Initially, we are led to believe that Sator is working for terrorists from the future who have lost all hope in humanity and blame the present generation for all its problems such as climate change and social disparity. Since they no longer have the algorithm to create a time inversion machine, they are paying Sator in time-reversed gold bars so that he can piece together the components to ensure the machine is eventually built. Sator pieces together the algorithm and drops the components into an underground vault in his nuked hometown, where the future terrorists will find it centuries from now.

However, Sator soon learns that he has terminal pancreatic cancer, and believes if he dies, then the whole world should die with him. After the algorithm is completed, Sator  link his time inversion machine to a dead-switch activated by his fitness tracker. Kat, Sator's estranged wife, is convinced Sator will carry out his plan in the past during their holiday to Vietnam, which was the final time Sator felt genuinely happy. After that day, Sator disappeared for awhile and reemerged out of nowhere with his plan to destroy the world. 

Tenet’s plan

With Priya's time inversion machine, Tenet members are able to travel back to the 14th of the month. They then travel to Sator’s hometown to stop his evil plan. Once there, Tenet splits into two teams; red team moves forward through time as normal, while blue team is time-inverted. This tactic is what is referred to as a ‘temporal pincer movement’. This creates a distraction battle that allows a splinter cell of led by The Protagonist to get hold of the algorithm. In the underground vault, the Protagonist finds Sador's henchman burring the algorithm with the dead body of a blue team Tenet member on the ground with the same red trinket that the Protagonist saw earlier in Kiev. As the henchman prepares to kill The Protagonist, the dead Tenet member is revived as he is time inversion and takes the shot instead. Now resurrected, the time-inverted Tenet member helps The Protagonist take the algorithm.

Sator’s fate

At the same time, Kat, now re-inverted, travels back to Vietnam with Mahir. Once there, she pretends to be her younger self while being with Sator to make sure he stays distracted while Tenet deals with his men. She shoots him and pushes him off his yacht, killing him right before the explosion at Sador's hometown. This means Sator never disappeared after their holiday in Vietnam, he was actually killed by Kat. The Protagonist, Neil and the head of Tenet's armed forces split the algorithm into three pieces, and promise to hide them away. As Neil turns and walks away, The Protagonist sees the red trinket on him, revealing him to be the masked gunman in Kiev and the dead time-inversed dead body that saved his life earlier that day. 

The truth about Neil

Neil reveals that he is actually a Tenet member from the future, who was recruited by The Protagonist himself. Although The Protagonist has only known Neil for a few days, Neil has known him for years. This means, Neil is moving backwards while The Protagonist is moving forward in time. Neil walks back into the time inversion machine to invert himself so that he can save The Protagonist's life, which means he knows this is his end. Before doing that, he leaves his piece of the algorithm with The Protagonist before time-inverting himself.

The truth about The Protagonist

In the last scene, Priya is shown trying to assassinate Kat since it is Tenet's objective to destroy any trace of time inversion knowledge. However, The Protagonist shows up and reveals that he will be the one to set up Tenet in the future, meaning he will be the one to recruit not only Neil but Priya and himself too. He then kills Priya, but lets Kat live.