Iron Man and Captain America: two core members of the Avengers, the world''s greatest super hero team. When a tragic battle blows a hole in the city of Stamford, killing hundreds of people, the U.S. government demands that all superheroes unmask and register their powers. To Tony Stark - Iron Man - it''s a regrettable but necessary step. To Captain America, it''s an unbearable assault on civil liberties.