The film starts out during World War II, when Captain America is fighting the villains of the film. The Captain is frozen in suspended animation, only to be revived in the twenty-first century by the American military, who are hoping that they can recreate the serum in Captain America's blood in order to create more super-soldiers.

Bruce Banner and his girlfriend Betty Ross are among the government scientists working to recreate the Super-Soldier serum. Banner has been taking a series of drugs to prevent his transformation into the Hulk, but wants to stop taking them because they interfere with his ability to work. Meanwhile, the revived Captain America has to get used to living in the twenty-first century, after going on an indoor rampage thinking he was being held prisoner. Nick Fury tries to persuade Thor, Giant-Man, Wasp, Iron Man and the Black Widow to unite under the leadership of Captain America in order to stop an attempt by Chitauri space aliens to take over Earth. Iron Man refuses since he "works alone".
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