
Continuity mistake: Right when Bella's transformation begins her hair is bushed above her shoulders then next shot her hair is under her shoulder, then when her hair is changing color it's back on her shoulder. (01:42:45)

Continuity mistake: After Renesmee's birth, there are two smudges of blood on Edward's right cheek. While Edward works to transform Bella, the blood spots appear and disappear between shots.
Answer: They want Alice because she can see into the future, which would be a significant advantage to the Volturi. Aro destroys other covens, sparing the one member who has some special ability.
raywest