After the Celestial Tiamut's emergence, now called "Celestial Island," sparks an arms race for adamantium, President Thaddeus Ross pushes for equal trade of the metal. Five months later, Ross enlists Sam Wilson and the new Falcon, Joaquin Torres, to stop a Serpent Society deal involving stolen adamantium. After completing the mission, Wilson introduces Torres to Isaiah Bradley for further training.
Ross calls Wilson, Torres, and Bradley to the White House, revealing plans to reform the Avengers. While addressing world leaders, a mind-control signal from the song "Mr. Blue" causes Bradley and others to attack Ross. Afterward, Ross has Wilson excluded from the investigation.
Determined to help Bradley, Wilson and Torres track the mind control to Samuel Sterns, a prisoner at "Camp Echo One" in Virginia. Sterns, exposed to Bruce Banner's blood, gained advanced intellect and is seeking revenge on Ross for reneging on a promise. Sterns orchestrated the adamantium sale and the mind control as retaliation.
Wilson and Torres confront Sterns, but the situation escalates as Sterns aims to destroy Ross’ legacy and start a war between the U.S. and its allies. Wilson and Torres intervene to prevent conflict with Japan, though Torres is injured. Wilson learns Ross is using gamma radiation pills to prolong his life, refusing to release Sterns to secure his continued survival.
Sterns surrenders, but before arrest, he triggers Ross’ transformation into a red Hulk, leading to a battle in Washington. Wilson manages to stop Ross, reverting him to normal. Later, Bradley is exonerated, Torres recovers, and Ross is imprisoned. Sterns warns Wilson of an impending attack in a post-credits scene.