After repelling the alien invasion of New York in "The Avengers," Thor returned to Asgard; Tony Stark (Iron Man) and Bruce Banner (the Hulk) drove off to go play in a lab somewhere, and Steve Rogers, aka Captain America, left to begin a quiet life in a middle-class apartment in Washington, D.C. -- doubtlessly having turned down lucrative book offers and speaking engagements as an unseemly cashing-in of a legacy people died to give him.

So when Nick Fury (Samuel L. Jackson), director of the espionage agency S.H.I.E.L.D., enlists his help to rescue a hijacked government ship, it's something to do and a chance to do good. He couldn't have imagined that he and agent Natasha Romanoff, the Black Widow (Scarlett Johansson), were being thrown into a web of intrigue evoking such 1970s political thrillers as "Three Days of the Condor," "The Conversation" and "The Parallax View" -- some of the inspirations for "Captain America: The Winter Soldier," the latest installment of the Marvel cinematic universe that opens Friday with Chris Evans reprising his role as Rogers.

A THROWBACK TO THE '70s

The notion of a superhero political thriller may seem jarring to those who haven't followed comics' auteurist blossoming over the past generation, but the filmmakers were merely tuning into the zeitgeist. "We were all reading the articles that were coming out questioning drone strikes, pre-emptive strikes, civil liberties -- Obama talking about who they would kill, y'know?" says Anthony Russo, co-director with his brother and filmmaking partner, Joe. "We wanted to put all of that into the film because it would be a contrast to Cap's greatest-generation ."

Indeed, says Christopher Markus, who with Stephen McFeely wrote both "Captain America" movies and is doing a third. "The Snowden didn't come along until May of 2013, and by that time we were six weeks into shooting. This kind of thing has been in the public consciousness since ... well, since Watergate," the impetus for those classic '70s political thrillers, says Markus. "Though as far as I know, we don't have the ability to kill 20million at a time," as posits the movie's central crisis, one complicated by an enigmatic Russian assassin, the Winter Soldier (Sebastian Stan).

"Nick's the kind of guy who deals with necessary evils," says Jackson, who reprises his Marvel Studios role as Fury. "So for him, having the gun pointed at us," he says metaphorically, "is as important as having the gun pointed at the enemy."

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The idea of a surveillance state -- embodied in the movie by three airborne aircraft carriers set to watch over the country like security cameras into the soul -- "is not a foreign concept to me," Jackson says. As a college student, he was active in the civil rights movement and knows well the FBI's wiretapping of Martin Luther King Jr., so "I'm not as surprised as the American public seemed to be last year when they realized the NSA was listening to their phone calls," he says -- by phone, coincidentally, from Los Angeles. "It was kind of like, 'You didn't know that?'"

Joining the movie universe is Anthony Mackie ("The Hurt Locker") as Sam Wilson, a post-traumatic stress disorder counselor Rogers befriends. He's also a former military pilot in a classified project situated between real-life wingsuits and the Iron Man armor, who finds himself again donning the Falcon project's winged, jet-powered exoskeleton, becoming in the process the Marvel movies' newest superhero.

"Sam Wilson is the only person who respects Captain America for who he is," Mackie muses. "He doesn't want anything from him, he doesn't ask him for anything. The first thing he does is, he tries to help him. So I think when you see that, it endears you to Sam, and when you see Cap being a superhero, struggling with his life, it endears you to Cap as well."

REDFORD SIGNS UP

Also new is Robert Redford as a senior S.H.I.E.L.D. official. "You get automatic '70s conspiracy-film gravitas when you hire Robert Redford," says Markus of the legendary star who's no stranger to the political thriller landscape ("Three Days of the Condor," "All the President's Men"). The role wasn't written with him in mind, Markus says, "because that's not the kind of thing you ever imagine is possible: 'Oh, yeah, we'll get Robert Redford. ... No way. When we found out it was Redford, we rewrote it with him in mind, because that's a whole persona you want to use."

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And his iconic continuity from the days of '70s political thrillers hammers home that the surveillance fears of that era have, well, come true. "I'm not naive enough to think that we don't need some of this stuff," says co-writer McFeely. "I don't pretend to know where that line of transparency should be. But when Dianne Feinstein has to go on the floor of the Senate and call out the CIA, something's wrong. We're dumb screenwriters -- we don't have the answer. But it was nice to be able to ask some of the questions in the context of a superhero story."

Cinema of the paranoid

The writers and directors of "Captain America: The Winter Soldier" said they found inspiration from these classic 1970s political thrillers filmed in the wake of Watergate:

The Conversation (1974) Audio-surveillance expert Gene Hackman inadvertently records plans involving murder and an apparent government-agency director (Robert Duvall) in this Francis Ford Coppola classic.

The Parallax View (1974) Reporter Warren Beatty discovers a corporation devoted to political assassination with "lone gunman" patsies.

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Three Days of the Condor (1975) After his field-office co-workers are assassinated, CIA analyst Robert Redford must elude a conspiracy reaching to the agency's top echelon.

All the President's Men (1976) This Oscar-winner was based on the actual events that led reporters Bob Woodward (Robert Redford) and Carl Bernstein (Dustin Hoffman) to expose the Watergate conspiracy.

Marathon Man (1976) Nazi war criminal Laurence Olivier tortures PhD candidate Dustin Hoffman, whose brother (Roy Scheider) works for a shadowy government agency called The Division.

Additionally, says co-screenwriter Christopher Markus, inspiration included "a little of 'The Manchurian Candidate' just in that kind of mental state" of a brainwashed character.