In March 1942, Nazi officer Johann Schmidt and his men enter the town of Tønsberg in German-occupied Norway, to steal a mysterious device called the Tesseract which possesses untold powers.
Meanwhile, in New York City, Steve Rogers is rejected for World War II military recruitment four times due to various health and physical problems. While attending an exhibition of future technologies with his friend Sgt. James "Bucky" Barnes, Rogers again attempts to enlist. Overhearing Rogers' conversation with Barnes about wanting to help in the war, Dr. Abraham Erskine allows Rogers to enlist. He is recruited in the Scientific Strategic Reserve as part of a "super-soldier" experiment under Erskine, Col. Chester Phillips, and British agent Peggy Carter. Phillips is unconvinced by Erskine's claims that Rogers is the right person for the procedure, but relents after seeing Rogers commit an act of self-sacrificing bravery. The night before the treatment, Erskine reveals to Rogers that Schmidt underwent an imperfect version of the procedure and suffered permanent side-effects, and told him to promise to remain a good man.
Back in Europe, Schmidt and Dr. Arnim Zola successfully harness the energies of the Tesseract, intending to use the power to fuel Zola's inventions, mounting an offensive that will change the world. Schmidt discovered Erskine's location and dispatches an assassin to kill him. In USA, Erskine subjects Rogers to the super-soldier treatment, injecting him with a special serum and dosing him with "vita-rays". After Rogers emerges from the experiment taller and more muscular, one of the attendees kills Erskine, revealing himself to be Schmidt's assassin, Heinz Kruger. Rogers pursues and captures Kruger, but the assassin commits suicide by swallowing a cyanide capsule before he can be interrogated.
With Erskine dead and his super-soldier formula seeminlgy lost, U.S. Senator Brandt has Rogers tour the nation in a colorful costume as "Captain America" to promote war bonds, rather than allow scientists to study him and attempt to rediscover the formula. In 1943, while on tour in Italy performing for active servicemen, Rogers learns that Barnes' unit was MIA in a battle against Schmidt's forces. Refusing to believe that Barnes is dead, Rogers has Carter and engineer Howard Stark fly him behind enemy lines to mount a solo rescue attempt. Rogers infiltrates the fortress of Schmidt's HYDRA organization, freeing Barnes and the other prisoners. Rogers confronts Schmidt, who removes his mask, revealing a red, skull-like visage that earned him the sobriquet "the Red Skull". Schmidt escapes and Rogers returns to base with the freed soldiers.
Rogers then recruits Barnes, Dum Dum Dugan, Gabe Jones, Jim Morita, James Montgomery Falsworth and Jacques Dernier to attack other known HYDRA bases. Stark outfits Rogers with advanced equipment, most notably a circular shield made of vibranium, a rare, near-indestructible metal. Rogers and his team successfully sabotage various HYDRA operations. The team later assaults a train carrying Zola. Zola is captured, but Barnes falls off the damaged train to his assumed death, into the icy waters. Using information extracted from Zola, the final HYDRA stronghold is located and Rogers leads an attack to stop Schmidt from using weapons of mass destruction on American cities and soon other major cities across the globe. Rogers climbs aboard Schmidt's aircraft as it takes off.
During the subsequent fight, the Tesseract's container is damaged. Schmidt physically handles the Tesseract, which incinerates him in a bright light and transports his remains into Asgard. The Tesseract falls to the floor, burning through the plane and falling to Earth. Seeing no way to land the plane without the risk of detonating its weapons, Rogers crashes it in the Arctic. Stark later recovers the Tesseract from the ocean floor, but is unable to locate Rogers or the aircraft, presuming him dead.
The Present
After seventy years, Rogers was defrosted and kept in a simulated 1940s environment to try and ease him into what was happening. Rogers awakens in the hospital room, but soon deduces from an anachronistic radio broadcast that something is amiss. He then escapes from the simulation and flees into what is revealed to be present-day Times Square in New York City, where S.H.I.E.L.D. director Nick Fury tells him he has been "asleep" for nearly 70 years. Rogers' only response is that he missed out on a dance he had promised to Peggy all those years ago.
A week after being defrosted, Steve Rogers found himself lost in a world that has moved on without him, and found it very difficult to adjust to this modern world. Nick Fury approached him with a mission to save the world. Fury informed him that the Asgardian mischief-god known as Loki had stolen the Tesseract and intended to use it to conquer and rule the Earth. Rogers wasn't thrilled to learn that HYDRA's secret weapon and power source had found its way into this era. Nevertheless, he quickly suited up as Captain America to help The Avengers defend Earth against Loki’s treachery.
After the cataclysmic events in New York with The Avengers team, Steve is living a quiet life in Washington, D.C., struggling to adjust to his new life, when he is drawn into a web of intrigue and danger to unmask a powerful but shadowy enemy that threatens to put the world at risk.
