It's all got something to do with a test that apparently doesn't have a lot of survivors. "That test you passed?" Martin Donovan's character says to him at one point. "Not everybody goes. Welcome to the afterlife."
His mission: Stop World War III. The word "tenet" is a password that ensures people take him seriously.
In one scene, Washington sees bullet holes in glass but says the shooting hasn't happened yet. If this movie is about reverse-engineering events by bending time and space, we're in for a crazy, awesome ride.
Other scenes in the new trailer shows not only numerous explosions, including a very big plane, but also conversations about the importance of reverse-engineering time to change the future.
So Tenet isn't about time travel, it's about the people who can manipulate time and thus future events. Maybe? We'll have to wait for more trailers to reveal clues to Nolan's sci-fi world where nothing seems to be set in stone.
Tenet is scheduled for theatrical release on July 17, 2020.
Also on a side note, it appears that Nolan will be showing "one of his iconic films to Fortnite this summer for a full length free screening for fans," so stay tuned for more details on that soon.