The Story of Clint Barton/Hawkeye (Marvel Cinematic Universe)

Chitauri Invasion: Destruction of P.E.G.A.S.U.S.

Having been recruited by Nick Fury to break into the Helicarrier and access the Avengers Initiative database in order to test its security, Hawkeye did as instructed and discussed the candidates with Fury, questioning the accountability of this team which included Iron Man and Captain America among others. Hawkeye was later called by Fury and stationed at the Main Facility of Project P.E.G.A.S.U.S. in order to guard the Tesseract. Before arriving on site, he did background checks on all the scientists working there, including Erik Selvig. Despite deducing that Selvig's back history was clean as he had no contacts who would be leaking information about their activities, Clint was ordered to stay at the facility to watch over the experiments on the Tesseract.

As Barton and Fury drove to the facility, he questioned Fury on not choosing Natasha Romanoff who was on a deep cover mission in Asia at the time, plus Fury knew not to isolate her in a bunker full of men. Fury then made it clear to him that not only is he guarding S.H.I.E.L.D.'S most important object in possession, but he needed to keep an eye on Selvig as he has been said to of been acting bizarre lately. Fury introduced him to Selvig and then left to catch a plane to the Arctic. As Fury left, Selvig asked Clint about his presence during the Battle of Puente Antiguo as he remembered him, not knowing that Loki was manipulating him.

Sometime later, the Tesseract began acting strangely so Fury and Maria Hill were called in to inspect the situations. Fury first spoke to Selvig and demanded a report about the Tesseract's energy levels before he spoke to Clint about his views on the situation, asking for a briefing on the team, Barton expressed his belief that Selvig and his team were not a threat to them. When Fury asked him if he believed that the Tesseract had been tampered with, Clint responded by saying that if there was tampering, it was not this end of the Tesseract, as he viewed the Tesseract as a doorway from space which could be opened from the other end, something Selvig and the other scientist weren't able to figure out.

The Tesseract suddenly opened a portal that brought Loki to Earth, who immediately attacked the base, killing several agents. Clint was just able to save Nick Fury's life from a blast of energy from Loki's Scepter. Loki then used his Scepter to alter and control the minds of Hawkeye, Erik Selvig, and a handful of S.H.I.E.L.D. agents. Under Loki's influence, Barton believed that he willingly worked for Loki and recommended that they evacuate the facility as the Tesseract was about to overload. Loki ordered Barton to shoot Fury before they departed.

Clint helped Loki steal the Tesseract and escape from the base towards S.H.I.E.L.D. Jeeps. However, Fury managed to survive due to wearing a Bulletproof Vest and warned Maria Hill of his betrayal, leading to a brief shoot out. They managed to get into a jeep and were chased by Hill until she became trapped under rubble when the facility imploded. Nick Fury managed to catch up with them and shot at them from a Helicopter, Loki shot the helicopter from the sky and Clint drove them away to safety.