Captain America and Black Widow Have a ‘Complex Relationship’ in Darker, Heavier ‘The Winter Soldier’

Marvel Studios — and the talent they employ — are notorious for being extremely secretive when it comes to details about upcoming Marvel movies. Ironically enough, it's Nick Fury, a key operative at the top secret government organization known as S.H.I.E.L.D., who's actually a bit loose-lipped.

Samuel L. Jackson dropped an interesting tidbit during the press conference for "Captain America: The Winter Soldier" at the San Diego Comic-Con as Chris Evans was discussing Cap's personal journey in the sequel, particularly his relationship with his fellow Avenger, Natasha Romanoff, aka Black Widow (Scarlett Johansson).

"Captain America is all about doing the right thing, but what in the modern world is 'the right thing'?," said Evans. "His sense of morality is challenged when he partners up with Black Widow, who's made a career out of compromising her morality for the sake of the mission at hand."

"She might have something of a 'whistleblower' in her future," added Jackson, to which Evans responded with a playfully incredulous "SAM!" and told him to shush.

But the question is: a whistleblower to what? Will Black Widow report her partner to S.H.I.E.L.D. authorities for some infraction, or is there corruption going on in S.H.I.E.L.D. that she goes up against? We can't wait to find out, but whatever the situation is (and we're betting on the latter), it sounds like Black Widow and Captain America are the right team for the job.

"Cap and Natasha develop something of an intimate friendship in this movie," said Johansson. "They both fight on the ground, because they can't fly. They have a similar fighting style. They both have their guard up, they both have trust issues. And they've both been working for 'The Man' for so long. It's a complex relationship."

[Related: Superhero Smooch! Scarlett Johansson and Chris Evans Kiss on 'Captain America' Set]

That "complex relationship" will apparently involve smooching at some point, as recent set pics revealed Evans and Johansson sharing a kiss. We have a feeling that's all part of whatever "undercover" mission they're on, though, as Cap seems like a one-gal kind of guy … even if his sweetie Peggy Carter (Hayley Atwell) was a part of his life back in the '40s and not in this brave new modern day world.

And it's that modern day setting that allows "Captain America: The Winter Soldier" to be a much different film than its predecessor.

"This film has a different tone, it's a political thriller," said Joe Russo, who co-directs the film with his brother, Anthony. "It's modern, edgy, aggressive. It's very heavy and very intense."

[Related: Hold Up! Captain America Fights His Friend Bucky Barnes in ‘Winter Soldier’?]

It sounds like quite a departure from the flag-waving first film, which Evans says gave Cap "the opportunity to serve," where as the new film is about "Well, who am I actually serving? Where's the line?"

While "Captain America: The Winter Soldier" promises to be a much darker outing than "The First Avenger," at least one cast member is lightening the mood with his own personal geek-out: Anthony Mackie, who seems genuinely thrilled to be a part of this world in the role of Sam Wilson, aka Falcon, a character very close to the hearts of the Brothers Russo as one of the first comic books they ever bought was "a Captain America/Falcon book," according to Joe.

"I love this character — Marvel is able to give such substance to a character without making it heavy or hokey," said Mackie. "He's a tactical expert … who can also fly! I'm looking to take down Iron Man so I can be the only flying Avenger."

Someone pointed out that Thor can also fly. "Thor doesn't fly — his hammer can fly!" said Mackie, which inspired applause from the room.

"Captain America: The Winter Soldier" hits theaters on April 4, 2014.

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