I know that David Lynch's movies are all very deep and hard to grasp and that probably there is no simple answer to this question, as there are different ways to interpret the movie.

Still I would like to know, what is the main story behind Mulholland Drive and what is the most common interpretation of what it is about?

I watched it several times and read the 10 clues that Lynch gave to unlock the riddle, but I still don't think I understand the movie. Is it all a dream? A metaphor? Whats with the character switch? Does the appearance of the strange old couple has something to do with sexual abuse? What about the monster in the alley?

What the hell is going on in Mulholland Drive?