A CIA operative, known as the Protagonist, participates in an extraction operation at a Kyiv opera house. After a successful but puzzling mission, he's captured by mercenaries but chooses suicide over betrayal. He awakens to learn the suicide attempt was a test of loyalty; he's subsequently inducted into a covert organization called Tenet. The Protagonist learns of a threat worse than nuclear holocaust: technology from the future that can invert the entropy of objects and people, allowing them to move backward through time. He's informed that this technology could lead to the destruction of the present, and his mission is to trace and stop this menacing technology.

To uncover the conspiracy, the Protagonist teams up with Neil, a British spy who is well-versed in the workings of inversion. Together, they start their journey with a clue leading to an arms dealer in Mumbai, who provides a pathway to a Russian oligarch named Andrei Sator. Sator communicates with the future and has a strained relationship with his estranged wife, Kat, a bargaining chip in the unfolding events. The duo navigates through a complex web of espionage, utilizing inversion technology to preempt Sator's moves. They travel through various international locales, engaging in high-stakes maneuvers that blur the lines between past, present, and future in a bid to thwart Sator's catastrophic plans.