1955: In a small Midwestern town, a pair of crooks rob a bank and gun down the sheriff. Suddenly Captain America appears and battles the thugs, but a black-clad woman in the crowd draws a gun and shoots Cap in the back. We discover that this is a training exercise in Russia, in a duplicate American small town, with Soviet agents playing the roles under the supervision of Natasha Romanova, the Black Widow.
In America at this time, Senator Joe McMurphy is delivering a fiery speech denouncing the evils of Communism and the American leaders who think they can negotiate with the Soviet Union. The real Captain America muses on the wisdom of McMurphy’s views while clobbering a gang of Commie spies. This Cap is not the original Steve Rogers, however, but a patriot who discovered the Super-Soldier Serum and volunteered to become the new Steve Rogers—and the new Captain America. CIA Agent Nick Fury is called before McMurphy’s Senate Committee and asked to give the names of men in the government he knows to have Communist leanings; Fury refuses, since he served with those men in the War and their service gives them the right to vote as they please. Later on TV, the news reports that German scientist Dieter Prochnow is offering a Nazi weapon to the highest bidder. Both the Americans and the Soviets are suspicious but neither can afford to ignore the possibility that it’s true.
Cap gives an interview to TV newsman Ed Murtaugh in which he endorses McMurphy’s patriotism but questions his tactics, saying that the Senator’s harassment of Nick Fury and other solid American is merely doing the Soviets’ work for them. The angry McMurphy retaliates by smearing Cap as a Communist in the media. That night, McMurphy’s aide Ray Khan cuts a secret deal with Prochnow for the weapon. Also that night, Steve Rogers breaks into McMurphy’s home and discovers a secret room full of proof that McMurphy is really a Russian spy. As Cap he reveals this info to Nick Fury, but Fury does not believe him—and finds him a poor substitute for the real Steve Rogers. Cap rushes to the airport where he manages to capture Khan but McMurphy gets away in his plane, having duped the US into paying a high price for the superweapon then stealing it for his Soviet masters. Cap parachute-drops atop the Senator’s jet and makes his way inside where he battles the villain’s henchmen. Cap recovers the briefcase with the weapon plans but McMurphy escapes by parachute.
Captain America is honored at a reception by President Eisenhower and later joins Nick Fury for a meeting with Natasha Romanova, the Black Widow. She wants to defect to the USA and offers McMurphy as a prize….
In the Russian "Midwestern town" used for training purposes, McMurphy is describing the delights of American life (women, the weather, women, Chinese food, women, etc.) to a new undercover agent, when Captain America comes up behind him, punches him out, and takes him back to the US for trial.