Bright headlights cut through a thick sheet of snow-flakes. A scientist, bundled as warmly as possible, treks through the sleet. Two other men, in matching black cold-weather uniforms, approach the scientist. He leads them to an excavation site which is easily the size of a football field; at the center of the site appears to be a giant wing and fuselage.

The black-suited men cut through the fuselage of the mystery craft and enter. Inside they find the remains of a massive, frozen ship. One of the men brushes away at the snow and sees a shimmering red, white, and blue shield encased in ice.

Norway, 1942: Two caretakers for an ancient Viking ruin listen as their town is overrun by Nazis. Suddenly the front door blasts open and in flood multiple Nazi agents. One of the caretakers is killed in the blast and the other frantically begs that the soldiers leave him in peace. They pay no attention to the old man and instead open the building's crypts one-by-one. They come to one sarcophagus whose lid is too heavy to lift.

A dark figure appears in the exploded entryway. Johann Schmidt (Hugo Weaving), a high-ranking Nazi and leader of a Nazi sect called "Hydra", nonchalantly enters. He crosses the room, comes to the difficult-to-open sarcophagus and easily pushes the lid free. Within he finds the skeletal remains of an old Viking clutching a glass cube (the Tesseract). The caretaker pleads for Schmidt to leave it.

Schmidt scoffs and tells how this cube would be the jewel of Odin's treasury if it weren't a fake. He smashes it on the floor and goes to the caretaker, asking where the real cube reposes. The caretaker initially refuses but under threat of harm to his family, he relents, gesturing to a hidden drawer across the room. Schmidt pries the drawer open and finds the real, glowing cube concealed within. Schmidt orders his men to level the city and then shoots the caretaker.

At a recruiting station in Brooklyn, Steve Rogers (Chris Evans), a 20-something, 90 lb, 5-foot tall asthmatic eagerly awaits the opportunity to enlist in the United States Army. The army doctor gives a once-over to Steve's medical file, which reads like that of a 90 year old man, and rejects Steve's application as the military 4-F.

Distraught Steve heads to the movies. He envies the enlisted men featured in the pre-show newsreel, and watches as other audience members tear up. A loud-mouthed, impatient movie-goer begins yelling at the screen "Start the movie! I didn't pay to see this crap!" Steve tells the man to shut up, and is surprised as the man turns around, stands up and towers above him. In the alley behind the theater the bully savagely beats little Steve.

Skinny Steve bravely fights back, but is easily overpowered. James "Bucky" Barnes (Sebastian Shaw), Steve's best friend, comes running to the alley. He swiftly kicks the bully away and tends to Steve, who is annoyed that Bucky showed up and got rid of the bully right as Steve got his second wind. "Bucky" is now an enlisted-man. His application was accepted and he's been assigned to the 107th infantry.

In a celebratory mood, Bucky invites Steve to go dancing with a pair of girls on a double date. Bashfully, Steve tags along. The four head to the World's Fair in NYC. While Bucky canoodles with his dates, Steve watches as a young Howard Stark (Dominic Cooper) unsuccessfully demonstrates a flying car. Steve breaks away from the group and goes to another recruiting station. Bucky catches up with him and asks how Steve intends to forge his application this time.

Unbeknownst to them both Dr. Abraham Erskine (Stanley Tucci) while passing by, eavesdrops on their conversation. He is fascinated by the gumption of Steve. Bucky wishes Steve good luck on his latest application and Steve heads in to the recruiting station for his fifth physical. Inside Steve sits on an examination table and grows nervous when an MP enters the room, and is soon followed by Dr. Erskine. Dr. Erskine has all of Steve's prior applications, and recognizing Steve's strong will and unwavering conviction, he accepts his latest application.

In a secret military installation high in the Alps of Germany, Johann Schmidt brings the glowing cube to Dr. Arnim Zola, his Hydra weapon specialist. The cube's seemingly limitless power enables Schmidt and Zola to power unstoppable energy guns and cannons.

Meanwhile, Steve has been enlisted into basic training under the careful watch of Dr. Erskine and Colonel Chester Phillips (Tommy Lee Jones). He and his platoon are told that they are candidates for the government's latest "Super Soldier" program. Phillips is unimpressed with Steve and is vexed by Erskine's interest in him. During basic training Steve meets a beautiful, but serious British officer Peggy Carter (Haley Atwell) who seems to pity Steve.

Despite being the smallest and weakest of the platoon, Steve demonstrates the greatest spirit and selflessness. Phillips, still unconvinced, tosses a grenade into the group, and is surprised as Steve alone leaps on top of it, willing to sacrifice himself, before discovering that the grenade was a dummy. Phillips concedes to Erskine's decision.