Thanks to the many times we've seen one book split into two films—it was vaguely annoying for Twilight, it'll be downright intolerable by the final Divergent movie—we're conditioned to think of the "Part 1″ of any series as the appetizer, the cinematic amuse-bouche you have to watch before waiting another year for the main course. It's very unsatisfying. Mockingjay—Part 1 is no different, with one big exception: It leaves you craving more, instead of feeling unfulfilled.
A lot of this is thanks to the fact that third installment in the franchise is set in an almost entirely different world than the two films before it. The Hunger Games and Catching Fire both put teenage hero Katniss Everdeen (the perpetually movie-saving Jennifer Lawrence) in an arena fighting other teens for survival. In Mockingjay she's been rescued from the frying pan and thrown into the fire, joining the civil war her acts in the Hunger Games inspired. (It's like Che Guevara in reverse: She was the face of the movement before she joined the revolution.)
Setting up this new battle means there's a lot of explaining to do—and while thanks to quick direction from Francis Lawrence it all gets done in a clean two hours, here's the even shorter version: After being extracted from the last Hunger Games at the end of Catching Fire, Katniss has been taken to the rebellion's underground bunker in District 13, a concrete and iron structure bathed in sci-fi grey.