We pick up right where we left off at in Part 1: Bella has birthed the Tooth Baby and survived via a bitey transfusion from Edward. Yep, not only is Bella a Cullen by marriage, she is also now a Cullen vampire. Just like in the book, it is unexplained why Bella takes so naturally to being a "newborn". Newborns are usually crazed and rabid with blood thirst, often for a long period of time, causing carnage with their newborn strength until they get a grip on the situation. Other than squeezing Edward a little too hard and almost chomping on an unsuspecting rock climber, Bella seems to have no problems. As the Cullens note proudly, she takes to being a vampire surprisingly well.
Meanwhile, Tooth Baby Renesmee, straight from the womb, is growing unnaturally fast. And she is also looking quite unnatural, especially at the infant stage. The first appearance of the baby caused just about every adult in the audience to shudder in discomfort at the not-quite-right CGI quality of the kid... creepy, but I'm sure not in the way that the filmmakers has hoped. (I think the only ones charmed were the 10-year-olds sitting behind me who cooed, "The baby is SOOO cute!!!") Even as Renesmee grows like a bamboo shoot, she is weirdly CGI-ed at her various ages until she finally ends up looking relatively normal by the time she morphs into 9-year-old-ish Mackenzie Foy.
Oh, and Jacob has imprinted on Renesmee. Nothing hotter than a grown man waiting for an infant to grow up so they can be together. (Ew.)
Anyway, the news of Renesmee's existence reaches the Volturi ancients in Italy, and they are none-too-pleased. Word is that they are coming to look for a fight in Forks, and the Cullens are outnumbered. The bulk of Part 2 has the Cullens reaching out to their vampire buddies around the world so that they have allies to watch their backs. Though there are about one beellllion cast members in this series, a few of the new additions spark up the proceedings, especially Lee Pace's shaggy rocker-vampire, and Rami Malek's wide-eyed, kind of sweet vampire who may as well have stepped out of The Last Airbender, with his element-manipulating skillz.
Oh, did I mention that Bella can produce a force field? Did I mention that the finale of this film (and series) may as well be The X-Men, with all of the mad skillz going on in the vampire world? That is one of the reasons the Volturi are so interested in the Cullens, and Michael Sheen (as old, powerful Volturi vampire Aro) once again delights as the only actor who really knows what movie he is in. Aro's interest in Renesmee is like a little kid reaching for a shiny toy. Try not to giggle (with the rest of the audience) at Aro's high-pitched maniacal laugh of joy.
For Twilight fans, there is plenty of Bella and Edward making out. Most of the beloved characters get a blip of screen time, if only to make an appearance. There is a big battle sequence for the climax which is the best part of the movie—it works the crowd's love of the characters, messing with the audience's emotions, while allowing for a satisfying climax which totally makes sense (as much as anything in Twilight does, that is). For the non-rabid fans, Part 2 is a weirdly slow movie that happens to have a good ending. But who cares? Romance wins, the audience wins, and all the haters can finally move on to the next pop-culture series to hate.