Tenet took Christopher Nolan over a decade to develop conceptually and more than five years to actually write. When it arrived on September 3, 2020, it became the first Hollywood tentpole to open theatrically during the COVID-19 pandemic — a decision Nolan personally championed against studio pressure to delay. The film grossed $365.9 million worldwide on a $200 million production budget, making it the fifth-highest-grossing film of 2020 despite the extraordinary market conditions. Nolan shot across seven countries (Denmark, Estonia, India, Italy, Norway, the United Kingdom, and the United States), using his regular cinematographer Hoyte van Hoytema on 65mm film and IMAX. The score was composed by Ludwig Göransson — replacing Nolan's longtime collaborator Hans Zimmer, who was committed to Dune — and the film was edited by Jennifer Lame, who had previously worked on Manchester by the Sea and Hereditary, replacing Nolan's long-serving editor Lee Smith. The film follows the Protagonist, a CIA operative played by John David Washington who is never given a personal name, as he is recruited into a covert organization called Tenet to stop Russian oligarch Andrei Sator (Kenneth Branagh) from using inversion technology to destroy the past at the direction of a future civilization. The central concept — inversion, a process that reverses entropy for objects and people, allowing them to move backward through time while still interacting with the forward-moving world — took Nolan two decades of thinking to develop into a story. The title itself is both a palindrome and an allusion to the Sator Square, an ancient Latin word puzzle whose five words — SATOR, AREPO, TENET, OPERA, ROTAS — Nolan used as a naming template for the film's key characters, companies, and settings.

The Sator Square is the film's most structurally elegant feature and the detail that rewards the most attentive viewers. The square is a real historical artifact — a five-word Latin palindrome reading the same in all four directions — and Nolan used all five of its words as design elements. Andrei Sator takes his name from the square's first word. His security company is named Rotas, the square's fifth word, and his freeport in Oslo operates under that name. The film's opening action sequence takes place at an opera house in Kyiv, connecting to the word OPERA. A forger named Arepo appears in the story. And Tenet, the square's central word forming a cross at its heart, is the name of the organization the Protagonist eventually discovers he himself will found. That last revelation is the film's deepest structural joke: the Protagonist spends the entire film being recruited into an organization that, from his temporal perspective, already exists, while from the film's complete perspective, he will create it. Inversion is the mechanism that makes this possible. A turnstile — the device used to invert people and objects — reverses the entropy of whatever passes through it, so that an inverted person moves backward through time from the world's perspective while experiencing time normally from their own. Inverted bullets move from impact point back into a gun. Inverted cars drive backward. Inverted people breathe through masks because ambient oxygen is moving in the wrong direction for their lungs. These rules are introduced gradually through Barbara (Clémence Poésy), a Tenet scientist who demonstrates them for the Protagonist early in the film. The Protagonist's unnamed handler and eventual closest ally Neil, played by Robert Pattinson, appears to be a contemporary new recruit — but the film's ending reveals that he has known the Protagonist for years from his own perspective, because a future version of the Protagonist recruited him long before the events of the film begin. The backpack Neil wears at the film's end is the same backpack seen on a masked figure at the Kyiv opera house at the film's start — meaning Neil died at the opera to save the Protagonist, and the Protagonist only understands this after the fact.

The Algorithm is the film's central MacGuffin: a device capable of inverting the entropy of the entire world, which would destroy everything in the past from the perspective of the people in the future who built it. It consists of nine pieces that the future hid across different points in the past, and Andrei Sator was tasked with reassembling them. Sator grew up in Stalsk-12, a fictional Soviet closed city in Russia, and was given bars of gold by the future in exchange for doing their work. He is terminally ill with pancreatic cancer, which gives him his nihilistic motivation: if he cannot survive to see the future, he sees no reason for the past to survive either. His plan is to assemble the Algorithm in Stalsk-12 on the day he dies, triggering a dead man's switch that will send the burial coordinates to the future. Kat (Elizabeth Debicki), Sator's estranged wife, is an art appraiser who authenticated a forged Francisco Goya painting for her friend Arepo, which Sator purchased to blackmail her into staying in the marriage. She becomes the Protagonist's most important human asset because she is the only person Sator has genuine emotional attachment to. The car chase in Tallinn, Estonia is the film's visual centrepiece — a complex bidirectional sequence where an inverted version of the battle is happening simultaneously with the forward-moving version, which the audience only fully understands on rewatching. The final battle at Stalsk-12 uses a temporal pincer movement: one team moves forward through time while a second, inverted team moves backward through the same window simultaneously, each gathering information the other cannot see. Ives, played by Aaron Taylor-Johnson, commands the forward-moving Red Team while Wheeler (Fiona Dourif) leads the backward-moving Blue Team. Kat, meanwhile, travels to Sator's last happy day — a family vacation on his yacht in Vietnam — and keeps him alive long enough for the mission in Stalsk-12 to succeed before he can send the dead man's switch signal.

The ending of Tenet reconfigures the entire film in a single conversation. Neil tells the Protagonist that from his perspective, they have known each other for years — that the Protagonist will, at some point in his future, recruit Neil and send him backward to key moments, including the Kyiv opera house, to protect the mission. This makes Tenet a closed causal loop: the Protagonist is the person who built the organization he was recruited into, sent the people who saved him, and set up the conditions for his own success without any external originating cause. It is a bootstrap paradox made structurally literal. Neil's death at the opera — saving the Protagonist from a locked gate inside the tunnel — happens at the beginning of the film for the audience but at the end of Neil's own timeline. He knows when they part at Stalsk-12 that his next step is backward to the opera house and his end. The film's moral weight sits in that knowledge, and in the Protagonist's inability to stop it because the event is already in both their pasts. The Protagonist and Ives agree to separate and hide the pieces of the Algorithm after the battle, ensuring the future cannot reassemble it. Priya (Dimple Kapadia), the arms dealer and Tenet operative who has been guiding events, plans to kill Kat to eliminate loose ends — but the Protagonist kills Priya first, protecting Kat and her son Max. The film ends with the Protagonist watching over Kat and Max from a distance, the world saved through a structure he will spend his future life building. Nolan has said the film was inspired by a feeling about how Sergio Leone approached Once Upon a Time in the West — trying to create a sense of remembered genre rather than documented genre. He deliberately avoided watching spy films during the writing process, relying instead on his own memories of the form.