"In its story, its wealth of symbolism, and its fascinating and ultimately compelling protagonist, Mulholland Drive is easily the most absorbing movie of which I am aware.
There are two main points to my view of Mulholland Drive's plot:
(1) Diane sees herself as a murderess, but her guilt is not as simple or straightforward as some of the scenes suggest. Her actions were a factor in the death of the brunette woman known as Rita in her dream and Camilla in her flashbacks/fantasies/daydreams, but they did not directly cause it.
(2) Diane has multiple personalities, a legacy of childhood abuse. These are a significant influence on the way she remembers and imagines the things we see in the movie."