The plot of the sci-fi movie directed by Christopher Nolan (of The Dark Knight, Batman Begins, Memento, The Prestige fame) is about entering peoples' minds/dreams through an injection. DiCaprio plays a CEO-type whose team work to enter the minds of other characters in order to retrieve/plant information.
Inception also stars Marion Cotillard as DiCaprio's wife, Juno's Ellen Page as a young college grad student named Ariadne, who is also DiCaprio's sidekick, and Joseph Gordon-Levitt plays Arthur, an associate working for DiCaprio.
Ken Watanabe will play the film's villain, a man named Saito, who is blackmailing Leonardo DiCaprio's character while Tom Hardy plays Eames, a member of DiCaprio's team. Cillian Murphy and Michael Caine complete the cast.
The film will release on July 16, 2010.