Two years after the Battle of New York,[N 1] Steve Rogers works in Washington, D.C. for the espionage agency S.H.I.E.L.D. under Director Nick Fury, while adjusting to contemporary society. Rogers and Agent Natasha Romanoff are sent with S.H.I.E.L.D.’s counter-terrorism S.T.R.I.K.E. team, led by Agent Rumlow, to free hostages aboard a S.H.I.E.L.D. vessel from Georges Batroc and his mercenaries. Mid-mission, Rogers discovers Romanoff has another agenda: to extract data from the ship’s computers for Fury. Rogers returns to the Triskelion, S.H.I.E.L.D.’s headquarters, to confront Fury and is briefed about Project Insight: three Helicarriers linked to spy satellites, designed to preemptively eliminate threats. Unable to decrypt the data recovered by Romanoff, Fury becomes suspicious about Insight and asks senior S.H.I.E.L.D. official and Secretary of Internal Security Alexander Pierce to delay the project.
On his way to rendezvous with Maria Hill, Fury is ambushed by assailants led by a mysterious assassin called the Winter Soldier. Fury escapes to Rogers’ apartment, and warns Rogers that S.H.I.E.L.D. is compromised. Fury is gunned down by the Winter Soldier, before handing Rogers a flash drive containing data from the ship. Fury is pronounced dead during surgery, and Hill recovers the body. The next day, Pierce summons Rogers to the Triskelion. When Rogers withholds Fury’s information, Pierce brands him a fugitive. Hunted by S.T.R.I.K.E., Rogers meets with Romanoff. Using data in the flash drive, they discover a secret S.H.I.E.L.D. bunker in New Jersey, where they activate a supercomputer containing the preserved consciousness of Arnim Zola. Zola reveals that ever since S.H.I.E.L.D. was founded after World War II, Hydra has secretly operated within its ranks, sowing global chaos with the objective of making humanity surrender its freedom in exchange for security. The pair narrowly escape death when a S.H.I.E.L.D. missile destroys the bunker, and realize that Pierce is Hydra’s leader within S.H.I.E.L.D.
Rogers and Romanoff enlist the help of former USAF pararescueman Sam Wilson, whom Rogers befriended, and acquire his powered “Falcon” wingpack. Deducing that S.H.I.E.L.D. agent Jasper Sitwell is a Hydra mole, they force him to divulge that Zola developed a data-mining algorithm that can identify individuals becoming threats to Hydra. The Insight Helicarriers will sweep the globe, using satellite-guided guns to eliminate these individuals. Rogers, Romanoff, and Wilson are ambushed by the Winter Soldier, who kills Sitwell. During the fight, Rogers recognizes the Winter Soldier as Bucky Barnes, his childhood best friend who supposedly fell to his death on a mission, but was actually captured and experimented upon after WWII. Hill manages to extract the trio to a safehouse where Fury, who had faked his death, is waiting with plans to sabotage the Helicarriers by replacing their controller chips.