Steve Rogers (Reb Brown) is a contemporary man whose father was a 1940s government agent. The very patriotic attitude of Steve's father earned him the nickname "Captain America." His father was later murdered. Rogers, a former Marine now making a living as an artist and traveling the countryside in a conversion van, is inspired by his father's story to sketch a super-hero. After receiving potentially fatal injuries in an attempt on his life intended to seem like an accident, he is administered an experimental chemical called the FLAG formula; FLAG is an acronym for "Full Latent Ability Gain," a kind of "super-steroid." (Rogers's father had developed the FLAG serum from his own glands.) The formula not only saves his life but enhances his strength and reflexes. These new abilities inspire Dr. Simon Mills (Len Birman), the research biochemist and intelligence official behind FLAG who was once a friend of Steve's father, to recruit Steve and give him a costume based on his drawing.
Steve Rogers (Reb Brown) is first shown sketching a portrait of a Mrs. Shaw (Susan French), who complains to him about a gang of muggers who have been stealing the proceeds from cashed Social Security (United States) checks; she denies having cashed hers. He bids her do this in order to set a trap for the muggers, and springs the trap as Captain America. In the meantime, a free-lance revolutionary terrorist calling himself General Miguel (Christopher Lee), planning to fight an unspecified war, kidnaps a Professor Ian Ilson (Christopher Cary) and forces him to resume his research in manipulative gerontology. Ilson has managed to formulate both a chemical that accelerates aging and the antidote to the same chemical, and Miguel, posing as the warden of a prison in Oregon near Portland, plans to use the chemicals in question to hold Portland hostage for a multimillion-dollar ransom. Ultimately Rogers and Miguel directly clash face-to-face, and when Miguel throws a glass bottle of the aging accelerant into the air, hoping it will shatter against Captain America's body, the Captain throws his shield into the air, where it shatters the bottle in such a manner that the aging accelerant splashes them both. However, as the Captain only received a minor amount and only ages a month. Miguel, on the other hand, ages to death in less than a minute.