Inland Empire is exceptionally strange. There is almost no comprehendable narrative, and where there is one, it is so sketchy and surreal that it is still difficult to follow. It is a moody, dark, 3 hour nightmare. It is a certified, hardcore mind-f*ck, leaving you with almost no sense of what you just watched, making it near impossible to decipher with just one viewing. I loved every minute of it.
Now, I know there are several theories about the plot floating around, and I have formulated my own after a repeat viewing. I'll start with the basic plot, that is actually completely coherent and developed for at least part of the film: An aging actress, played by the glorious Laura Dern, is cast in a film that could have the potential to rekindle her career. She is cast alongside a notorious womanizer, who is warned not to try with her on account of her possessive and violent husband. The film is apparently cursed, as revealed by their director, a criminally underutilized Jeremy Irons. The rest of the film is up to the imagination as to what it all means.
I have formulated a theory of my own. While it is very possible that the film does in fact only occur in the mind of Dern's character, I like to believe that it follows a normal (if convoluted) narrative. As Dern becomes more and more melded with her character in the film Blue Tomorrows, she loses her grasp with reality and delves into fear and apprehension.
The subplot of the two Polish lovers is quite obviously of the two previous leads of the Polish version of the film. They are both killed by a mysterious man, an omen of death to anyone who plays the lead in the film. He hypnotizes Theroux's character's wife into killing Dern, but this event really only occurs in Tomorrows. More about him is revealed later in Lynch fashion, but I'm not going to spoil the ending.
There are several other subplots, better described as hallucinatory sidenotes, but one could go on for days discussing them and their meaning. The important thing is that Lynch has given us yet another dazzlingly impossible puzzle to sort out. Hats off to you, Mr. Lynch.