How does Gandalf escape from the cage that imprisoned him at the end of The Hobbit - The Desolation of Smaug? Is he saved by Radagast?
(I’m afraid I have not yet read the book.)
Gandalf's journey to the Necromancer's realm is mentioned briefly, in passing, but we don't really get much detail about it. It seems, however, that he didn't run into nearly as much trouble in the book version of events.
Now that we know the answer to this. (spoilers)
Galadriel, Elrond, Saruman, and Radagast come to Gandalf's aid. Elrond and Saruman duel with the spirits of the nine men given rings of power, the soon to be nazgul (after easily disposing of the orc that was holding him there). Sauron makes an appearance, and Galadriel uses her ring to banish him to parts unknown.
Short clip (Doesn't have much, just the very beginning of the fight)
I think this is my favorite scene of the movie.
I believe Galadriel and others will come to help him. In the books Galadriel brings down the wall of Dol Guldur