The Asgardian Loki encounters the Other, the leader of an alien race known as the Chitauri. In exchange for retrieving the Tesseract,2 a powerful energy source of unknown potential, the Other promises Loki a Chitauri army with which he can subjugate the Earth. Nick Fury, director of the espionage agency S.H.I.E.L.D., and his lieutenant Agent Maria Hill arrive at a remote research facility during an evacuation, where physicist Dr. Erik Selvig is leading a research team experimenting on the Tesseract. Agent Phil Coulson explains that the object has begun radiating an unusual form of energy. The Tesseract suddenly activates and opens a portal, allowing Loki to reach Earth. Loki takes the Tesseract and uses his scepter to enslave Selvig and several agents, including Clint Barton, to aid him in his getaway.
In response to the attack, Fury reactivates the “Avengers Initiative”. Agent Natasha Romanoff is sent to Calcutta, India to recruit Dr. Bruce Banner; Coulson visits Tony Stark to have him review Selvig’s research; Fury approaches Steve Rogers with an assignment to retrieve the Tesseract. While Barton steals iridium needed to stabilize the Tesseract’s power, Loki causes a distraction in Stuttgart, Germany, leading to a confrontation with Rogers, Stark, and Romanoff that ends with Loki’s surrender. While Loki is being escorted to S.H.I.E.L.D., Thor, his adoptive brother, arrives and frees him hoping to convince him to abandon his plan and return to Asgard. After a confrontation with Stark and Rogers, Thor agrees to take Loki to S.H.I.E.L.D.’s flying aircraft carrier, the Helicarrier. There Loki is imprisoned while scientists Banner and Stark attempt to locate the Tesseract.