Who is John Walker in The Falcon and the Winter Soldier?

This drove him to take the last remaining vial of the Flag Smasher's super soldier serum, enhancing his strength but making him unstable in the process, as demonstrated by his deadly outburst at the end of episode four.

However, the series finale saw John show a glimmer of true heroism and his newly formed partnership with the mysterious Contessa Valentina Allegra de Fontaine suggests his story is far from over.

Below, you can find an overview of the character's comic book history and where he might go next in the Marvel Cinematic Universe.

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Who is John Walker?

John Walker burst onto the pages of Marvel Comics back in 1986, introduced as a former soldier in the United States Army who wished for people to look up to him as a hero as they did his brother, who died in the Vietnam War.

He had not achieved this goal by the time he was honourably discharged from active service, which led him to seek out the Power Broker, a figure in the Marvel Universe who can give people superhuman abilities via experimentation.

With his newfound super-strength, Walker took on the alter-ego of Super Patriot and was originally depicted as a villain, starting a fight with Captain America as he wanted to be the hero synonymous with the USA.

Although he failed to best Steve Rogers in hand-to-hand combat, Walker went on to become a national celebrity after preventing a terrorist attack in Washington DC while in his Super Patriot guise.

This act of heroism made him the government's choice to be the next Captain America after Steve temporarily abandoned the mantle, with Sam Wilson being considered for the job but ultimately overlooked due to racial discrimination.

Walker's actions as the new Captain America were to be more strictly controlled by the US government than Steve Rogers ever had been, while they also provided him combat training from experts including Taskmaster (soon to be introduced in May's Black Widow movie).

Unfortunately, it doesn't go well for him as he is both a less competent and more brutal operative than his predecessor, known for beating his villains close to death in several instances.

This issue only worsens when Walker's parents are murdered by a terrorist group, a devastating turn of events that very nearly drives him completely insane.

Ultimately, he returns the mantle of Captain America to Steve Rogers and the government publicly fakes his death, while entering him into a witness protection programme.

He is later brought back into the fold to be a government plant on the West Coast Avengers, led by Hawkeye, under the not-so-subtle codename USAgent – which he has generally stuck with ever since.

The character has been a consistent recurring presence across the Marvel Universe in the decades that have followed, staying on the side of the heroes most of the time.

However, his violent tendencies and fragile mental state continue to be problematic, as well as his frosty relations with the other Marvel heroes – particularly Hawkeye, with whom he has maintained a feud since his days on the West Coast Avengers.

Is John Walker the new Captain America?

He is – or at least, he was. As introduced at the end of the first episode (and more extensively in episode two), John Walker was selected by the US government as the new recipient of Steve Rogers' shield. In the show Walker didn't immediately have his villainous comic-book backstory, instead depicted as a decorated soldier (apparently, he's the first person in history to win three Medals of Honor) known for counterterrorism and hostage rescue missions.

In fact, he was so capable that his body was tested by the government at MIT, where he tested "off the charts in every category," whatever that means. All this led to John being named the new Captain America instead of Steve Rogers' choice Sam Wilson, with his role doubling as a kind of PR figurehead as well as an agent of US Government interests. As in the comics, Walker was accompanied in his missions by sidekick Battlestar, aka Lemar Hoskins, though in this story he's an old army friend of Walker's.

Unfortunately, Walker's story took a darker turn in later episodes of the series. After a series of humiliating defeats Walker is upset by his lack of success as Captain America, and manages to get his hands on a vial of Super-soldier serum from Karli Morgenthau during one of their battles.

Following this, Walker is strong enough to go toe-to-toe with the Flag-smashers – but that's not enough to save his friend Lemar from an accidental mid-fight death, sending Walker over the edge as he beat one of the Flag-smashers to death with his shield in the eye of the public's mobile phone cameras. Following this, Walker was disarmed, stripped of his role and discharged from the military.

In the post-credits scene of episode five, Walker decided to go rogue and take on Karli (Erin Kellyman) after she caused Lemar's death, forging his own shield from scrap metal to aid his mission. However, when his opportunity to confront her finally came, he prioritised saving a van filled with hostages over his own personal grudges, suggesting that there is still a heroic side to his nature and that he hasn't been consumed by his negative traits.

This might be why he has been headhunted by the mysterious Contessa Valentina Allegra de Fontaine, played by Julia Louis-Dreyfus, who has managed to get him a new costume and official codename: USAgent. Some fans have speculated that he could be in-line for a position on either the Thunderbolts or the Dark Avengers, two teams with storied histories in Marvel's comic book universe. Whatever the case, it seems safe to assume we haven't seen the last of John Walker.

Read our latest The Falcon and the Winter Soldier review, plus learn more about The Falcon and the Winter Soldier cast, including who Helmut Zemo, Sharon Carter, or Patriot is or who the mysterious Power Broker could be, and never miss an episode with our The Falcon and the Winter Soldier release schedule.

The Falcon and the Winter Soldier launches on Disney Plus on Friday 19th March. You can sign up to Disney Plus for £7.99 a month or £79.90 a year now. Take a look at the rest of our Sci-fi coverage or visit our TV Guide to see what's on tonight.