Parallel universes (version 2)
Mulholland Dr. is an enigma for any spectator. However, without demerit of other possible perspectives of interpreting this movie, I find indispensable to sustain the validity of a hypothesis in which all the pieces fit without forcing them. Viewed this way, I believe that the hypothesis which makes the most complete sense is that of the "parallel universes", that is to say, realities that exist in different times and spaces, but with many elements in common and, in this case, one created in function of the other one, to complete certain objectives.
The first one that we see (but not the first one that happens) is the "luminous dimension", that tells us Betty's story (Naomi Watts), who arrives to Hollywood, via airplane, to take a vacation on their aunt's apartment and to prove her luck in the film industry. There she meets Rita (Laura Harring) who has arrived there accidentally, after surviving an attempted murder and losing her memory. They like each other immediately and the friendship soon grows to intimacy. In the meantime, Rita begins to remember some things: the name "Diane Selwyn" and the "Club Silence". The girls, when visiting the remembered places, discover respectively the corpse of unknown suicide Diane Selwyn and a mysterious blue box that opens with the blue key that Rita had with her since the beginning. Uncannily, they both disappear and the sequence concludes.
The "dark dimension" begins then, with greater narrative agility, and we see, in transmuted identities, Diane Selwyn (Betty) and Camilla Rhodes (Rita) as lovers in crisis. Diane, with overwhelming evidence of the betrayal that Rita inflicts upon her, plans vengeance and, seemingly, she hires a hitman. After receiving the confirmation that the deed has been done, Diane, tormented by hallucinations and remorse, commits suicide.
The film is evidently designed to produce confusion in the spectator, in such a way that only when he has put the events in chronological order it's possible to fit together all the puzzle's pieces.
Fundamentally, what happens first is the story of Diane and Camilla, the demise of their relationship and subsequent murder of the former and suicide of the latter. Then appears the key character in the whole plot: the Cowboy, who says to Diane's dead body, with a benevolent greeting: "Time to wake up!". The film goes immediately to the story of Diane's awakening before having died, but the "real" or chronological scene is Diane's landing (already transmuted in Betty) in Los Angeles, her compensatory reality where she gets ready to fix the things that went wrong in the first one. The purpose and objective of this "luminous" reality is none another than to reconcile Diane with her dear "Camilla" (now called Rita). Once this is completed, a mysterious blue box gives the means to conclude the story.
Let us notice that in this second reality the characters, atmospheres and situations of the first one return, many of them in a quick way in order to condense them in a vital enough space to obtain the purpose of that existence. It is worthwhile to argue against certain opinion, which affirms that this second reality is a dream. The presence of the Cowboy denies this theory, as does all those scenes in which Betty is not present nor can suspect them; in addition, several characters only exist in that reality to protect the happy life that Betty has been blessed with, and they are aware of it. This explains why the old couple smile with satisfaction after leaving Betty in the city, why aunt Ruth makes no big deal of Rita entering her apartment, why Betty's first audition is plagued with a fake atmosphere ("director" Bob's character is specially amusing).
Finally, a symbolic element that agrees with all that has been mentioned above is the outlandish show presented in the Club "Silencio", especially the performance of Rebekah del Rio: she sings and dies at mid song (song that, by the way, is the final symbol of the encounter and reconciliation of Diane/Betty with Camilla/Rita), nevertheless, the voice continues until the end, in the same way that Diane's life ends midway, but continues until completing its destination.