While we had heard so much about the film, this is the first time we got to know anything about its plot. 

While we still do not know anything concrete about the plot, the trailer shows that the film has something to do with time travel and stopping World War III.

You can watch the trailer here. 

Now the trailer might have released, but Warner Bros. is planning on releasing a longer version of it, to be played before Star Wars: The Rise of Skywalker in the theatres.