Two years after the Battle of New York, Steve Rogers is adjusting to life in the modern world while serving as an agent of S.H.I.E.L.D. in Washington, D.C. Despite his efforts to adapt, he feels out of place in a world far removed from everything he once knew. During his morning runs, he repeatedly crosses paths with Sam Wilson, a former pararescue airman now working as a counselor for veterans struggling with trauma. The two quickly form a bond over their shared experiences as soldiers trying to find purpose after war.

Steve is soon called into action by Natasha Romanoff for a mission aboard the hijacked S.H.I.E.L.D. vessel Lemurian Star. Alongside a STRIKE team led by Brock Rumlow, Steve successfully rescues hostages and neutralizes the pirates led by Georges Batroc. However, he discovers that Natasha had a separate, secret mission from Nick Fury to extract encrypted data from the ship. This revelation plants the first seeds of distrust in Steve, who is troubled by the secrecy surrounding S.H.I.E.L.D.’s operations.

Back at headquarters, Fury attempts to reassure Steve by showing him Project Insight, a controversial defense initiative involving three advanced Helicarriers capable of eliminating threats before they even act, using predictive algorithms. While Fury sees it as a necessary measure in a dangerous world, Steve views it as a violation of freedom, believing it represents fear and control rather than protection.

As Steve tries to process these concerns, he reconnects with his past by visiting an elderly Peggy Carter, now suffering from dementia. Their interaction is bittersweet, reminding Steve of everything he has lost. Meanwhile, Fury grows increasingly suspicious when he is unable to decrypt the data retrieved from the Lemurian Star. He approaches Alexander Pierce, a high-ranking official and trusted ally, requesting a delay in Project Insight’s launch.

Before he can act further, Fury is ambushed by assassins disguised as police officers. After a high-tech pursuit through the city, he is attacked by a masked figure known as the Winter Soldier, who demonstrates extraordinary skill and a cybernetic arm. Though severely injured, Fury manages to escape.

Fury seeks out Steve, warning him that S.H.I.E.L.D. has been compromised from within and cannot be trusted. Moments later, the Winter Soldier attacks again, shooting Fury through the wall. Before losing consciousness, Fury gives Steve a USB drive containing the stolen data and urges him to trust no one. Shortly afterward, Steve’s neighbor reveals herself as Sharon Carter, an undercover S.H.I.E.L.D. agent assigned to protect him.

When Steve pursues the assassin, he is shocked to find that the Winter Soldier can catch and throw his shield with ease before escaping. Fury is declared dead, and Steve is summoned by Pierce for questioning. Sensing danger, Steve withholds critical information, which leads Pierce to label him a fugitive. Soon after, Steve is ambushed in an elevator by STRIKE operatives, but he fights his way out and escapes.

On the run, Steve reconnects with Natasha, who has taken the USB drive. Together, they attempt to unlock its secrets and trace its origin to an abandoned military base—Camp Lehigh, where Steve once trained. There, they uncover a hidden facility containing the preserved consciousness of Arnim Zola, now existing as a computer system. Zola reveals a devastating truth: Hydra, the organization Steve once fought, has secretly infiltrated S.H.I.E.L.D. over decades, manipulating global events to create fear and justify authoritarian control. Before they can act on this information, the facility is destroyed by a missile strike.

Steve and Natasha seek help from Sam Wilson, who reveals he has access to experimental flight gear known as the Falcon suit. Together, they capture a Hydra operative, Jasper Sitwell, who explains that Project Insight is Hydra’s plan to use predictive algorithms to eliminate millions of potential threats—including individuals like Tony Stark, Bruce Banner, and even people who have done nothing wrong but might one day oppose them.

Before they can act, they are ambushed by the Winter Soldier. During the fight, Steve manages to unmask him, revealing the shocking truth: the assassin is Bucky Barnes, Steve’s best friend, long thought dead. Brainwashed and reprogrammed by Hydra, Bucky does not recognize Steve and escapes after a brutal confrontation.

Captured by Hydra forces, Steve, Natasha, and Sam are rescued by Maria Hill, who reveals that Fury is still alive, having faked his death. Together, they devise a plan to stop Project Insight by replacing the Helicarriers’ targeting systems with override chips.

As the Helicarriers launch, Steve broadcasts a message exposing Hydra’s infiltration of S.H.I.E.L.D., urging agents to resist. Chaos erupts within the organization as loyalties are tested. Natasha infiltrates the Triskelion using advanced disguise technology, while Fury confronts Pierce. When Pierce attempts to escape and silence the World Security Council, Fury kills him, ending Hydra’s leadership within S.H.I.E.L.D.

Meanwhile, Steve and Sam assault the Helicarriers. Sam is forced out of the fight after sustaining damage, leaving Steve to face Bucky alone. As the Helicarriers begin targeting millions of people, Steve refuses to fight his friend, instead appealing to his memories. He allows himself to be beaten, insisting that he will not abandon Bucky. This act of loyalty triggers something within Bucky, who hesitates.

Steve succeeds in placing the final override chip, causing the Helicarriers to target and destroy each other. As the massive structures collapse, Steve falls into the water below. Bucky, conflicted and partially remembering his past, saves him before disappearing.

In the aftermath, S.H.I.E.L.D. collapses as its secrets are exposed to the world. Fury goes underground, officially declared dead, while Natasha faces public scrutiny for her role in revealing the truth. Steve, now free from S.H.I.E.L.D., chooses a new mission: to find Bucky and restore his identity. Sam, choosing to stand by him, agrees to help.

Elsewhere, Hydra remnants continue their work. Baron Strucker experiments with Loki’s scepter, unlocking mysterious powers in two enhanced individuals—hinting at new threats to come.