timdiggerm said:
It's pretty clear from the way that Vader looks at the Emperor, looks at Luke, looks at the Emperor, looks at Luke, and then yells "NOOOOOO" that he's in it to save Luke.
He yells what??
The thing is, the mask hides a lot. It's a blank slate upon which you can write your own personal interpretations and wishes.
He looks at the Emperor, thinking, "I do not want to take this guy on alone. That's what I brought Luke here for. Part muscle and part cannon fodder."
He looks at Luke and thinks, "This guy is not turning. He is not fighting back. He's gonna die and then I'm stuck subservient to Pruneface forever."
He looks back at the Emperor, thinking, "Screw it, it's now or never. Maybe I can get him over to that convenient pit before he fries the bejeezus out of me. Beats the alternative."
If he yells "NOOO" it's pretty much a non-sequitur any way you look at it.