The evil Loki, accompanied by an army of extraterrestrials called the Chitauri, is in pursuit of a powerful object known as the Tesseract. Nick Fury, director of the espionage and law enforcement agency S.H.I.E.L.D. activates a plan he calls the "Avengers Initiative": bring together Earth's greatest superheroes in case of an emergency. Now the only thing standing in the way of Loki's rule are the Avengers: Tony Stark, the self-proclaimed "genius, billionaire, playboy, philanthropist" known as Iron Man for his technologically advanced suit of armour; Steve Rogers, the World War II veteran known as Captain America, who was frozen in ice for several decades; Thor, the Asgardian hammer-wielding god of thunder and brother of Loki; Dr. Bruce Banner, a scientist who turns into a powerful green monster called the Hulk when angered; Natasha Romanoff, S.H.I.E.L.D. spy otherwise known as Black Widow; and Clint Barton, a master of archery also referred to as Hawkeye.