Where in the story does movie #2 end?
Hobbit #2 ends with Smaug flying out of the mountain on the way to kick the crap out of Laketown.
Fundamentally, Hobbit #3 is based on the couple of chapters of the book after this which is fricking preposterous.
Oh, some other shit was added as well, of course. In Hobbit #2, Gandalf is captured by the Necromancer/Sauron when he is investigating Dol Guldur. In Hobbit #3, Galadriel, Elrond, Saruman and Radagast come and free him, fighting off the Nazgul and Sauron - for some reason Galadriel does her demonic funny voice/glowing blue thing again which makes Sauron flee to Mordor. Saruman knowingly says he will deal with Sauron. Yeesh.