"What If... Captain America and Bucky Had Both Survived World War II?"
On a divergent, parallel world, Steve Rogers and his teenaged partner, Bucky Barnes still attempt to intercept a booby-trapped drone plane launched by Baron Zemo. In this reality, Rogers manages to deactivate the bomb before it explodes.
The partnership endures beyond the war. Bucky grows from adolescent to man, but there eventually comes a parting of the ways.
Steve Rogers is approached during the Cold-War era by President Lyndon B. Johnson to head a new counter-intelligence agency named S.H.I.E.L.D., in place of Nick Fury, who was killed during the Korean War. Steve declines the offer, not wanting to hang up his old Captain America boots yet, but proffers Bucky's name for the role.
Bucky leads an effective campaign to smash the evil Hydra organization, but the leader escapes to plot retaliation anew.
A royal rumpus with the rampaging Hulk leads to the rescue of Rick Jones. Bucky convinces Steve it's time to hand over the mantle to a younger man, and thus, a new Living Legend is born. Barnes becomes the new Captain America, while Rick Jones adopts Bucky's old uniform to partner him. Steve finally becomes director of S.H.I.E.L.D.
Sharon Carter's still destined to fall in love with Captain America, albeit Bucky Barnes, not Steve Rogers. Sharon hopes to get Bucky to retire after one last operation to obliterate Hydra.
That last job reveals Zemo as the Supreme Hydra who had escaped previously. Zemo's hatred of Captain America had sustained him some thirty years after the war had ended. Such wanton emotion conspires to take both the lives of the Nazi mastermind and the man currently wearing the red, white and blue costume.