Steve Rogers was a small, weak 90-pound asthmatic American boy living in Brooklyn. He tried to join the American army in World War II but was rejected every time. After seeing Rogers’ keenness, Abraham Erskine offered Steve a chance to be more than just a man using the Super-Soldier serum developed by Erskine and Howard Stark’s machine. After this, Steve became improved on all fronts, and acquired the alias ‘Captain America’. He himself freed hundreds of soldiers from a German camp and was then seen as a hero. His main enemy was Johann Schmidt or ‘Red Skull’, a psychotic leader of the Nazi weapons division named HYDRA. Rogers has a shield made of vibranium which deflects any and all projectiles. Rogers hijacked a plane built by Schmidt with the aim to destroy all the capital cities of the world. He overpowers Schmidt and crashes the plane into the Arctic sea to stop the destructive force of the plane, causing him to freeze and not age until he is uncovered in the 21st century. Nick Fury informs Rogers that he'd been "asleep" for nearly 70 years.
A week after being defrosted, Steve 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.
Rogers met with Agent Phil Coulson; a loyal Captain America fanboy;, Natasha Romanoff and Bruce Banner, the scientist who attempted to recreate the super-soldier serum but instead created the Hulk. Rogers was given a new uniform and sent to Stuttgard, Germany, where Loki had been sighted. Captain America arrived just in time to battle Loki, but found outmatched and had to be rescued by Iron Man/Tony Stark, the son of Howard Stark. While travelling back to the Hellicarrier, Thor emerged in an attempt to take Loki back to Asgard, only to end up in a fight with Stark, which Rogers himself broke up. Rogers protected himself from a blow by Thor's mystical hammer Mjolnir with his unbreakable shield, ending the fight and forming a truce with the thunder-god.
Back at S.H.I.E.L.D. headquarters, Stark and Rogers felt a potentially violent friction between the two of them and Rogers found himself taking up a leadership position. Rogers was angered by the discovery that S.H.I.E.L.D. had plans to use the energy of the Tesseract to build weapons as a detterent against extraterrestrials. As the Avengers became argumentative over how to confront the imprisoned Loki and the differences between them, the Helicarrier was attacked. Rogers helped Stark restart a failed engine.
The death of Agent Coulson during Loki's escape and the learning of the Avengers Initiative led Rogers and Stark to make the decision of ending the Avengers' association with S.H.I.E.L.D.. Captain America led the Avengers against the Chitauri invasion on New York and arrested Loki, who had been hindered by the Hulk. Rogers and the other Avengers greeted Thor farewell as he took Loki and the Tesseract back to Asgard, and knew that the Avengers would form again when this level of catastrophe were to occur again. Rogers rode off on his motorcycle to discover the modern world he was now a part of.
Rogers, having been given two years adjusting to life in the 21st century, made a list of everything he needed to catch up on that he had missed whilst being frozen. He encountered Sam Wilson during a routine jog around Washington, D.C. The pair quickly developed a strong bond as both were military men trying to cope with civilian lifestyles.
Rogers joined Natasha and the Strike agents, led by Brock Rumlow, to liberate a S.H.I.E.L.D. vessel, the Lemurian Star, which had been taken over by pirates, led by Georges Batroc, who were holding hostages, including Agent Jasper Sitwell. Rogers, in a new Stealth Captain America outfit, dived out of the jet armed only with his shield and no parachute. He landed in the water and climbed onto the ship, taking out every mercenary with his speed, strength and shield using various fighting techniques.
The Strike agents defeated the remaining pirates and rescued the hostages while Batroc tried to run but was caught by Steve. They fought on the deck of the ship, with Batroc getting quickly back up on his feet even when Steve managed to take him down. Steve continued the fight and knocked Batroc down for good.
During the mission, Steve found Natasha extracting files from the ship's computer using a S.H.I.E.L.D. flash drive. He called her out on this as she was supposed to be helping Rumlow get hostages out and placed the whole mission in jeopardy not knowing she had been assigned to this by Fury.
Later, at the Triskelion, Steve confronted Nick Fury about the motives behind Natasha's task. Fury knew Steve wouldn't be comfortable with it, so he asked Natasha. Fury reminded Steve that he can't trust anybody, even those who work closely with him.
Fury took Steve into an elevator down to the underground level where there were three new state-of-the-art Helicarriers being worked on as part of Project Insight, an operation that would connect the Helicarriers to spy satellites used to prevent any possible terrorist attacks. This was a reaction to the events that took place in New York, but Steve saw it as more of an aggressive means of tyranny rather than a form of protection for people.
Conflicted, Steve visited the Smithsonian to check out an exhibit dedicated in his honor. Among the displays were mannequins with costumes of Steve's Howling Commandos, and a tribute to his old friend James 'Bucky' Barnes, whom Steve saw fall to his death. Steve watched a video of his old love, Peggy Carter, in which she commemorated Steve on his actions as Cap. He later visited an ill and elderly Peggy, who had since been married and had children.
Steve went to visit Sam, who was counselling other veterans suffering from PTSD. After the group meeting, Sam revealed to Steve that despite losing his friend Riley in combat, Sam still loved flying. He asked Steve what makes him happy, but Steve can't answer.
That night, Steve went back to his apartment, and after chatting with his pretty neighbor, Steve heard music from his apartment as he cautiously entered, grabbing his shield for protection. He found an injured Fury sitting on his couch. Out loud, Fury said that his wife had kicked him out, but he showed Steve through text on his phone that anybody could be listening. Before he could say anything else, Fury was shot three times. Steve looked out the window for the shooter. Fury handed him the flash drive and told him not to trust anybody.
The neighbor came in, armed with a gun, she is really an agent of S.H.I.E.L.D. who was tasked with keeping an eye on Steve. She tended to Fury as Steve ran after the assassin, smashing through the walls to catch up. He threw his shield, but the assassin caught it with one swift move then threw it back. When Steve looked up, the assassin had disappeared.
Arriving at the hospital with Maria Hill and Natasha, Steve observed as the doctors performed emergency surgery on Fury in an attempt to save his life only for him to flatline during the surgery. Natasha asked for a description of the shooter, Steve told her that he was strong, fast and had a metal arm. Rogers picked up that Natasha knew more about the shooter but was unable to question her further when Rumlow told him that he was needed back at S.H.I.E.L.D. HQ immediately. Before leaving Natasha questioned Steve on why Fury was at his apartment, Steve attempted to deny knowing the reason but Natasha pointed out he was a terrible lair. Realizing she was right, Steve chose to hide the flash drive in a vending machine.
Inside the Triskelion, Steve met Alexander Pierce, who told him about his rich history he had with Nick Fury, as well as Fury using Batroc and his pirates as a diversion to retrieve intel on Project Insight. Pierce demanded that Rogers reveal why Fury came to him. Rogers told Pierce that Fury's last words were "Not to trust anyone."
Rogers left via the elevator heading to the operations section only to be joined by Rumlow and a few members of the Strike team, as the elevator descended more agents entered the elevator boxing in Rogers, who immediately took note and realized that they were tasked to capture him. He gave them the option to leave before the fight started but the agents attempted to subdue Rogers with magnetic restraint cuffs. With one arm pinned up against the wall Rogers managed to single handedly defeat every agent even Rumlow who was using electric baton tasers. He then freed himself with his shield. To evade capture by another unit, Rogers jumped forty stories and landed in the main hall using his shield to protect his fall.
Rogers attempted to escape on his motorcycle when he was confronted by a Quinjet that began to fire upon him. Using his cycle Rogers launched himself upon the aircraft and with his shield he took out the wings and engine before landing on the ground with ease using his shield to stabilise him.
Disguised, Rogers returned to the hospital to retrieve the flash drive when he noticed that the USB was gone. Natasha appeared behind him. Angrily Rogers demanded to know what she knew, Natasha told him that the masked shooter was known to the intelligence world as The Winter Soldier and she had encountered him before in her past. Rogers concluded that there must be valuable intel on the flash drive which was why The Winter Soldier was tasked with assassination of Fury.
Rogers and Romanoff, disguised in civilian garb, headed to a local Washington D.C. mall into an Apple store where Natasha attempted to read the file on a laptop but found the data encryption impossible to crack and knew that in the next nine minutes S.H.I.E.L.D. would close in on their position. She decided to find the original source using a satellite tracker to pin point the data origins which revealed a place in New Jersey all too familiar to Rogers. As the Strike force unit closed in on them, Steve and Natasha kissed and their public display of affection allowed them to evade the Strike team.
Steve and Natasha commandeered a jeep heading towards New Jersey. During the drive, Natasha teasingly asked Steve if that was his first kiss since 1940's and if he had experience. Steve assured her it wasn't. Arriving at Camp Lehigh, Rogers remembered his training with the Strategic Scientific Reserve. Natasha, meanwhile, searched for the source of the signal but was unable to find one believing they had hit a dead end. Rogers noticed an ammunition bunker in the wrong location and upon further investigation they discovered that the bunker hid a secret underground office that appeared to have been the foundational roots of S.H.I.E.L.D. with pictures dedicated to the founding members Chester Phillips, Howard Stark and Peggy Carter. Steve found a secret elevator behind a storage shelf and Natasha used a decoder to access the outdated control panel. They took the elevator further underground into a secret room full of a massive computer mainframe, Natasha rebooted the system using a modern looking USB slot and put the flash drive in.
The system awoke and a digital version of Arnim Zola appeared on the monitor, he revealed what had occurred after his capture by the Captain and his allies and when his body was un-savable, he transferred his mind into software and in that process he helped in forming S.H.I.E.L.D. after War World II but also set in motion sleeper HYDRA agents to infiltrate and take over the organization and for the last seventy years HYDRA had been running S.H.I.E.L.D. as a means to gain an advantage and bring the world to its knees.
Zola had been working on an algorithm for HYDRA to use to eliminate their current threats and potential future threats. He told Steve and Natasha that some of the deaths of S.H.I.E.L.D.'s leaders had been as a result of HYDRA using their assassin, showing them a picture of Howard Stark, implying that his death might not have been an accident. Zola was also involved in the creation of The Winter Soldier program. Romanoff asked what Project Insight was, Zola responded by telling them that they had run out of time, he was stalling. A missile strike hit the Bunker. Rogers pulled the grate of a manhole up and, with Natasha, jumped into it and used his shield to protect them as debris enclosed around them. With all his strength, Rogers pushed free of the debris then carried Natasha out to safety before the Strike force appeared on site.
Returning to Washington, Rogers went to Sam Wilson, asking for a place to stay temporarily. As he and Natasha cleaned themselves up, Rogers noticed that she was uneasy so he approached her. She said that the revelation of HYDRA infiltrating S.H.I.E.L.D. made it seem no better than her days as a KGB operative. Realizing that Rogers selflessly rescued her, she asked him if it was the other way around would he trust her to save his life. Rogers replied that he would now and that he was glad to know who they were fighting. Sam entered the room and offered them breakfast.
In the kitchen, Rogers and Romanoff began to piece together HYDRA's plan and realized that Alexander Pierce was their leader and that Jasper Sitwell was also a sleeper agent. They tried to work out how to grab and interrogate Sitwell. Sam offered his help by using a military EXO-7 Falcon winged jetpack.
With Sam's aid, Rogers attempted to interrogate Sitwell about his presence on the Lemurian Star and involvement in Project Insight by holding him at the edge of the rooftop. Sitwell was unconvinced that Rogers would drop him because it wasn't his style. Rogers agreed so Black Widow kicked Sitwell off the ledge instead, sending him plummeting down to the street below. On the rooftop Steve and Natasha engage in some playful banter when Sam flew upwards with Sitwell and dropped him on the roof, ready to talk.
Sitwell revealed that Project Insight was a means for HYDRA to eliminate current and future potential threats that have been foreseen by Zola's Algorithm with the usage of the three Insight Helicarriers' advanced targeting system they would be able to eliminate them but also millions of innocent people around them would be casualties.
Acting quickly, Rogers, Natasha and Sam headed down the highway intending to go to the Triskelion and use Sitwell to bypass security. Unbeknownst to them, they were being tracked by the Winter Soldier who boarded the rooftop of the vehicle and with his bionic arm pulled Sitwell out the window and into the oncoming truck on the opposite side instantly killing him.
While holding onto the roof of the car, The Winter Soldier fired his gun below into the car. Rogers took control of the break switch causing The Winter Soldier to be thrown clear across into the pavement. He used his bionic arm to slide to a stop. He then stood up without a scratch on him. The Winter Soldier approached the Humvee from behind and pushed them directly into his path, he leapt on top of the car and ripped off the steering wheel. Seeing that they were losing control of the car, Rogers used his shield against the side door as a slide with Natasha and Sam with him as the car veered off and flipped over in the middle of the highway.
The Winter Soldier then fired an RPG at Romanoff, but Rogers pushed her out of the way and used his shield to deflect it, sending him flying off the bridge and onto the streets below right into a bus.
A crew of mercenaries fired at the bus attempting to pin him down But Rogers managed to evade the incoming gun fire and retrieve his shield using it to deflect bullets and a gun turret. Having dealt with the mercenaries, with assistance from Sam, Rogers went after The Winter Soldier who was hunting Romanoff who he had injured her with a gun shot to the shoulder and pinned her behind a car.
Armed with his mighty shield, Rogers engaged in a ferocious battle with The Winter Soldier who appeared to be his equal as they counter each others swift kicks and punches in combat. The Winter Solider, armed with his bionic arm and a knife, proved to be a challenge for Rogers yet in the course of the battle, Steve managed to partly damage his bionic arm and rip the mask off his face and made the shocking discovery of The Winter Soldier's real identity - Bucky Barnes. The Winter Soldier aimed his gun at Rogers. Sam swooped in and kicked the Winter Soldier off balance just as Natasha fired a RPG in his direction and he disappeared.
Rogers was bewildered by this startling revelation, just as the Strike force unit and police closed in on their position and arrested Rogers, Romanoff and Wilson. Inside the transport back to the Triskelion, Rogers surmised that Zola experimented on Bucky when the 107th unit was captured and that's how he survived falling from the train. Rogers, filled with guilt and remorse, took responsibility for what happened to Bucky. Natasha told him it's not his fault before she bled out from her wound. Sam asked a guard to take her to a doctor for treatment. One of the guards pulled out a baton taser and struck the other guard, revealing herself as Maria Hill. Using the Mouse Hole device, she freed Rogers and the gang and brought them to a secret facility where she revealed to them a recuperating Nick Fury that was severely injured. Fury revealed he faked his death by using a anti stress serum, developed by Bruce Banner, that lowered his heartbeat to only one per minute so that he would appear dead. Fury and Hill told them that Project Insight was only hours away and that they had to act quickly. The Helicarriers would hover in a triangle, connected, targeting all its targets before firing. The only way to prevent this was to use three special chips that would take away S.H.I.E.L.D.'s control over the Helicarriers. Fury intended to save S.H.I.E.L.D. but Steve firmly insisted that the organization be dismantled after all the corruption it had fallen under.
As Pierce reunited with the World Security Council to witness the launch of Insight, Steve, who had donned his old WWII Captain America uniform, infiltrated the Triskelion and revealed by loudspeaker the truth of HYDRA influencing S.H.I.E.L.D. and prompted every clean agent to stand up against HYDRA. Steve and Sam later managed to replace the controller chips of two of the three Helicarriers. But in the third Helicarrier, Cap found himself against the Winter Soldier. Against his own will, Steve fought Bucky, while attempting to trigger his memory at the same time. Steve tries to get the chip in place with only seconds left before Project Insight will initiate he gets shot multiple times by Bucky. He manages though and Hill take control of the other Helicarriers. Hill accessed the Helicarrier's systems to modify their targets to themselves, thus they started firing at each other, and slowly fall apart in mid-air. As the third Helicarrier was collapsing, Steve discovered Bucky trapped under rubble. Steve saved him, but Bucky still attempted to kill him. Steve refused to fight against him, and let himself be almost beaten to death. Before Steve passes out he promises Bucky to be with him until the end, a promise Bucky gave Steve decades ago. This halted Bucky's attack as Steve fell off the Helicarrier and into the Potomac River. Slowly remembering his past, Bucky rescued Steve and left him in the side of the river before disappearing.
Steve later awoke at the hospital. Fully recovered, Steve encountered Fury and said goodbye to him. Natasha also met up with Steve, and gave him a dossier on Bucky and the Winter Soldier program. He and Sam then decided to try to track down Bucky.