well, the tagline is "Hell wants him. Heaven won't take him. Earth needs him"
since i am a devout catholic, this may sound a little textbook to some. in the catholic church, one is deemed to go straight to hell if he/she commits suicide. John Constantine, Keanu Reeves, does commit suicide at a young age after his parents put him through tests to question his sanity. however he in fact does not die and has a second chance at life and to do good. This way he can enter heaven. basically the gist of the story is that hell somehow needs to find something or somebody to give birth to the son of Lucifer. Lucifer is the devil himself who founded hell and is the direct opposite (for simplicity's sake) of God.
To skip over lots of details, Constantine's main objective in his second life is to get out of "purgatory" and into the Big Man's good books.
i loved this movie, really go check it out. Rachel Weisz is also really good and after a lot of thinking ... Balthazar is GAVIN ROSSDALE OF BUSH!
-fb