Before there was light, there was darkness. And in that darkness lived the Dark Elves.
Is that sentence too silly for you to handle? Then Thor: The Dark World isn't meant for you. A sequel to Marvel's 2011 hit Thor, Thor 2's makers apparently decided that the best course of action is to take everything that made the original the camp hit it was, and ramp it all up to eleven.
It's been two years since the events of Thor; the titular hero (Chris Hemsworth) has spent the years bringing peace to the nine realms, as well as thwarting the plans of his brother, Loki (Tom Hiddleston), which you saw in The Avengers. However, when Jane (Natalie Portman), Thor's human love interest from film #1, becomes infected with a gooey, mystical substance called æther, it awakens the ancient Dark Elves, who seek to eradicate all nine realms and plunge the universe back into darkness.
I promise you that it really as campy as it sounds. In fact, going over plot details seems almost an afterthought at this point; this is a Marvel movie, which means that there's a very specific formula to which the movie will adhere. Heroes will be threatened, plans concocted, betrayals planned and thwarted, heroines endangered and then empowered—and as always, Hiddelson will absolutely steal every scene he appears in.
Luckily for disbelief-suspending viewers like myself, that recipe's not stale yet.
Since at this point you should know exactly what kind of movie you're getting into, I think it's fine to indulge in some movie meta-commentary here: it's interesting that the reviews for Thor and Captain America are almost exactly the same as of this writing (77% and 79% scores on Rotten Tomatoes), because ...