In "Thor," Loki - Odin's (Anthony Hopkins) adopted son and Thor's adopted brother - kills Odin to take over the throne. He then casts out Thor to Earth.
Thor lands in a desert, and is immediately ran over by a PhD cosmology student (Natalie Portman) and her Norwegian professor (Stellan Skarsgard), who were on their way to study a strange cloud in the cosmos. When they realize that Thor is who he says he is, Skarsgard's character, who has grown up with Norse mythology, can't quite deal with it and goes out on a drinking binge.
And even though we see Thor on Earth, AICN has confirmed that his alter-ego Donald Blake will not make an appearance.
The script closes with a 5-page battle, showing off Thor's and Loki's different fighting styles. Thor being very much about raw strength, while Loki being much more about motion, grace and intelligence. The closing battle will be the first thing that director Kenneth Branagh will film.
Apparently Thor will handle Loki, but will not kill him, since Loki goes on to be one of, if not the key bad guy in "The Avengers" movie.
In the first 20 minutes of the new film, Loki brainwashes Bruce Banner to gain control of the Hulk for his own evil deeds. When the green monster goes on a rampage, Thor, Iron Man and Captain America are forced to assemble.