Bollywood actress Dimple Kapadia might have a blink-and-miss appearance in the trailer of Christopher Nolan's much-hyped "Tenet", but the city of dreams -- Mumbai -- shines bright in the clip, hinting that the city plays an important role in the time travel and spy drama.

The film has been described as "an action epic evolving from the world of international espionage", but there is a time travel twist -- making the trailer mind-boggling.

It left fans guessing about what happened in the past, in present and what will happen in the future, just like Robert Pattinson's character asks John David Washington's character in the trailer, "what happened here?" and gets the response "it hasn't happened yet".

The trailer gives a sneak peek into the world of "Tenet". It has gripping, gritty and high-octane sequences, but doesn't reveal any solid plot points.

The trailer opens in Mumbai with Washington and Pattinson hanging from a highrise building, with a voiceover stating: "We all believe we'd run into the burning building. But until we feel that heat, we can never know."

It then leads to Washington collapsing after struggle with someone, as he says: "You chose to die instead of giving up your colleagues". Cut to a sequence in a hospital where Martin Donovan's character says "That test you passed, not everybody does. Welcome to the afterlife".

There are many hints about the plot. At one point, Clemence Poesy's character said: "As I understand it, we're trying to prevent World War Three", and in another instance Washington's character questions "Nuclear holocaust?" and a voice then says: "No, something worse".

"All I have is the word tenant. It will open the right doors and some of the wrong ones too," informs the voiceover, teasing how the title of the film weaves the story together.

There are multiple scenes shot in Mumbai, mostly showing the lead characters in action and trying to fight evil. Then there's Dimple Kapadia's character in a shot where she is telling someone: "You have to start looking at the world in a new way".

There's a car chase scene, involving Washington and Pattinson's characters. When a car goes upside down, the voiceover mentions: "Don't try to understand it. Feel it." That seems to be the theme of the film.

The trailer ends with the words, "Time Runs Out", flashing on the screen.

Nolan shot the film in Mumbai in September. The film also stars Elizabeth Debicki, Aaron Taylor-Johnson and Kenneth Branagh. It is slated to release in July 2020.