The Dark Knight is the sequel to Batman Begins, aka Batman Begins 2. Here's the plot.
Batman and James Gordon join forces with Gotham's new District Attorney, Harvey Dent, to take on a psychotic bank robber known as The Joker, whilst other forces plot against them, and Joker's crimes grow more and more deadly.
Official teaser. It really is a teaser, seeing that it reveals nothing except about a minute of dialogue.
This fan-made trailer combines the teaser (which shows nothing) with some footage and pictures, making it even better than the offical teaser.
[Link: Dark Knight at IMDB]