The story unfolds as Thaddeus "Thunderbolt" Ross (Harrison Ford) takes the stage as the newly elected President of the United States, delivering a compelling promise to the audience that they will confront unprecedented threats together. However, the media paints a less flattering picture, highlighting Ross's volatile temper, with lingering blame directed at him for the destructive clash between the Hulk and Abomination in Harlem, further complicating his strained relationship with his daughter, Betty Ross (Liv Tyler).
Five months later, Sam Wilson/Captain America (Anthony Mackie) is actively engaged in a mission in Oaxaca, Mexico, alongside Joaquin Torres/Falcon (Danny Ramirez), operating on directives from Ross to tackle the mercenary group known as the Serpent Society, led by the cunning Sidewinder (Giancarlo Esposito). During an intense confrontation at a church, Captain America showcases his impressive combat skills, utilizing his shield and wings to fend off the mercenaries. However, while Cap manages to thwart Sidewinder’s hostage scenario, he has to contend with a larger foe, giving Sidewinder the chance to slip away. Meanwhile, Joaquin, equipped with his Falcon suit, tracks down additional mercenaries and intercepts a crucial package scheduled for a mystery buyer.
Upon reporting a successful mission back to Ross, Sam and Joaquin return to Baltimore to train under the watchful eye of Isaiah Bradley (Carl Lumbly). Ross later extends an invitation for the trio to attend a notable event at the White House. While Isaiah air his reservations about Sam working with a government that has failed them, Sam reassures him that positive changes are on the horizon.
As they attend the event, Sam is unexpectedly summoned by Ross for a private discussion regarding the potential relaunch of the Avengers where Sam would assume leadership. Despite his hesitations, mainly due to Ross's past management of the Sokovia Accords, Ross exhibits confidence in their collaborative future. During the gathering, Ross speaks to guests about ongoing mining operations at Celestial Island, where the discovery of adamantium is being negotiated for international treaty purposes—this coincides with the very package Sam and Joaquin managed to recover.
Suddenly, chaos erupts as Ruth Bat-Seraph (Shira Haas), a trusted security advisor and ex-Black Widow, springs into action when Isaiah and several other men fall victim to mind control, launching an assassination attempt on Ross. In a frantic chase instigated by Sam, he successfully convinces Isaiah to surrender just as he regains his senses.
Seeking clarity, Sam investigates further by confronting Ross in his bunker, where Ross expresses doubt over his involvement in the case, maintaining that Sam is too emotionally invested. An unsuccessful visit to Isaiah leads Sam to determine that the situation is dire, prompting him to recruit Joaquin's help to analyze surveillance footage from the attack. They uncover alarming evidence of a blinking device on the attackers' phones right before the incident, indicating a larger conspiracy at play.
The stakes escalate when Sidewinder ambushes Sam, leading to a fierce battle where Sam ultimately subdues him. The next phase involves confronting Samuel Sterns/The Leader (Tim Blake Nelson), the mastermind orchestrating the events behind the scenes, who reveals his thirst for revenge against Ross. With the confrontation only intensifying, Ruth joins forces with Sam and Joaquin, ultimately leading them to expose some shocking truths about the gamma pills that Ross is using to extend his life.
Tension mounts as world leaders lose confidence in Ross's capabilities, propelling Sam to confront him about his connection with Sterns. The conversation escalates as Ross reveals his deteriorating health, forcing him to rely on Sterns for gamma-laden pills. This revelation leads to a perilous situation involving international military actions as Ross's schemes spiral out of control, transitioning into a confrontation where he transforms into the Red Hulk due to overwhelming stress and rage.
An intense showdown ensues, resulting in destruction and chaos that threatens to dismantle the White House itself. Sam, striving to deescalate the situation, uses his strength and wits to remind Ross of his humanity, ultimately leading him back to his senses and out of his monstrous form.
As the dust settles, Isaiah is released from prison, rekindling his relationship with Sam amidst rebuilding efforts at the White House. Sam’s journey brings him to a significant encounter with Bucky ([Sebastian Stan]) who inspires him to believe in himself as a leader in this chaotic landscape. Unbeknownst to them, danger still lurks as Sterns ominously foretells future threats emerging from other worlds and universes during a visit from Sam, leaving a dark shadow over the resolutions achieved and hinting at challenges yet to come.
