-By Ethan Alter

Once upon a time, the only things a summer blockbuster typically required for box-office success were a pair of glamorous movie stars, an exotic setting and a plot with an enjoyable blend of action, comedy and romance. In the past few years, though, the rules have changed dramatically. These days, the season's big-budget behemoths must come equipped with a host of new features to ensure profitability, among them characters with built-in brand awareness, a number following the title, and a grim sensibility designed to make the proceedings grittier and more "real." These elements are on display in the majority of this summer's offerings, from Iron Man 2 and The A-Team to The Last Airbender and The Twilight Saga: Eclipse.

And then there's a movie like Knight and Day, which studiously avoids them all. Instead, this action-comedy caper, which stars Tom Cruise and Cameron Diaz and was directed by blockbuster neophyte James Mangold (whose previous credits include 3:10 to Yuma, Walk the Line and Cop Land), arrives in theatres on June 25 offering an original story about a woman (Diaz) who meets a devilishly handsome mystery man (Cruise) only to discover that 1) he's some kind of James Bond-like secret agent and 2) she's been targeted by the same crew of bad guys that are chasing him. What follows is a globe-trotting adventure full of explosive action set-pieces that are laced with a healthy dose of comedy. Oh yeah, and several romantic sparks fly too.

In other words, the Fox release is the kind of rollicking star-powered summer movie that would have seemed a sure bet a few years ago, but now is perceived as something of an outlier in a season that's almost exclusively reserved for sequels, remakes and big-screen versions of comic-books, videogames and old TV shows. Indeed, aside from Knight and Day there are really only two other original properties in the marketplace this summer, Phillip Noyce's Salt and Christopher Nolan's Inception, both of which appear to have a harder edge than Mangold's jaunty chase picture.

Mangold is well aware that his first attempt at a big summer movie seems out of step with the times. "We only realized recently, looking at what's out there this summer, that we're kind of an oddball," says the 46-year-old filmmaker, on the phone from his Los Angeles office. "But during my career, I've always run a little bit against the current trend and I do think there's [room for] another kind of large-scale entertainment that isn't quite so serious. My main goal with Knight and Day is really an old Hollywood goal: to create a wonderful journey of wish fulfillment with two of the most glamorous and capable actors alive. It's a movie meant to give joy and take you on a wild ride that isn't hollow and filled with empty calories. We're going for something that's fun, but also crafted—something that's not just continuous stimulus, but also has a wonderful set of ideas behind it. And that's a classic Hollywood journey that you don't see much anymore."

The story of Knight and Day's journey to the screen is almost as complex as its twist-filled plot, the exact details of which are being kept closely under wraps. The movie started its life over five years ago as a spec script entitled All New Enemies penned by Patrick O'Neill and went through several name changes (including Wichita and Trouble Man) and cast line-ups (Adam Sandler, Chris Tucker and Eva Mendes have all been previously linked to the project) before it found its way to Mangold's desk in early 2009. "I read a draft that Scott Frank had written and really responded to it," he remembers, adding that Diaz was already attached at that point while Cruise was still circling the film. "I thought it still needed a good amount of work, but I was really excited by some of the core ideas in it as well as the idea of Tom being in the picture. I felt that this was an incredibly persuasive role for Cruise and the kind of movie I really wanted to see him in."

What Mangold specifically wanted to coax out of the star was the kind of the subtle, almost accidentally comic performance he gave in Rain Man. "I wouldn't call Rain Man a comedy, but watching Tom's gears seize up as he's challenged by Dustin [Hoffman] is part of the joy of that movie. My favorite films on his resume are those where you can sense his incredible intensity pressing up against irrationality—he's got to make sense of stuff that makes no sense. Seeing him wrestle with that creates a wonderful comic friction and that's what I was trying to tap into here."

Mangold's pitch finally persuaded Cruise to come aboard and the two of them, along with Diaz, threw themselves into re-shaping the script to fit the movie they wanted to make, which the director describes as being in the tradition of North by Northwest and Charade. "In the early drafts I read, the film was more of a standard comedy with less action in it. But the concept I had was to make a movie that felt big, epic, adventurous and spectacular, but also very loose-limbed and improvisational. I didn't want there to be a sense of moment-to-moment predictability about it."

That loose-limbed approach began with the screenwriting process; Mangold reveals that he started working on the script in March of ’09 and only finished a few weeks ago while the movie was in the editing room. "I don't believe in having a fully locked script," he says. "I didn't have one on 3:10 to Yuma and I didn't have one on Walk the Line. The idea of a locked script supports a compartmentalization of the business that's mainly created for labor divisions and preventing lawsuits. The reality is that a film's narrative is always being shaped during writing, shooting, on-set explorations of a scene and in the editing room. An editor can have as much effect on the narrative as a huge rewrite of the screenplay.

"The movies I wanted to emulate—Charade, Tootsie and The Apartment, which only had half a script when they started making it—have the spontaneity of a babbling brook. They found their own way instead of following the Syd Field model of 'hit these points.' That said, we always knew how the movie ended and what the middle points were, because everyone needs an idea to work from. But there were days where we'd come in and do exactly what we'd planned and then there were days we'd come in and do something wildly different."

According to Mangold, one of the key scenes featured in the film's trailer came about as a result of the improvisational atmosphere he encouraged during shooting. "That moment in the diner where you see Tom saying 'I'm the guy' and Cameron goes 'He's the guy'—that was something we came up with on set. It's not only a wonderful scene in the film, but it's also the centerpiece of the marketing campaign! There's a heat that comes from actors who have different working styles; Tom always wants to figure everything out and Cameron is really loose and playful. That produces a natural sense of spontaneity; you never know where a scene is going to go."

Of course, allowing for improvisation in a small, dialogue-driven scene is one thing. It's much harder to give the actors room to find the laughs when they're in the middle of a large-scale action sequence involving gunfire, hand-to-hand combat and elaborate stunts. "Directing a movie like this is a little like steering a very large ocean liner—you can't turn on a dime," Mangold admits. "However, a shot can turn on a dime. Meaning that within the context of a chain of 30 shots that may have been planned and budgeted with sets constructed, explosives set, computer shots set and rigs built, you could still end up saying, 'If we change this brick, this can happen.'"

Perhaps the scene that best typifies the blend of comedy and action that Mangold sought to achieve throughout is a battle aboard an airplane that finds Cruise fending off an army of assassins while an unsuspecting Diaz is in the restroom. "When I was shooting that scene, it occurred to me that I could have made an over-the-top battle on an airplane to the death using every seat cushion and luggage rack and oxygen mask. But to do it in a way so that the action is both hilarious and credible was really exciting. The trick to this kind of movie is to achieve a magical tone where some of the stuff that happens is ludicrous and some stuff is quite realistic, but the audience never gets hit with so much stuff that's ludicrous that they reject the reality of the film or so much stuff that's real that they lose their sense of comedy and fantasy."

The funny thing about blockbusters that aren't designed to be franchises is that they can often turn into franchises anyway—just look at what happened to Pirates of the Caribbean. Still, Mangold insists that the thought of helming Another Knight and Day never occurred to him during shooting or now that the picture is wrapped. "I literally finished the movie yesterday, so I'm not really prepared to answer the [sequel] question," he says with a weary laugh. "Besides, when you're making an original film it's getting ahead of yourself to think that way, because you have to deliver on the first one before those questions come into play."

With no new project immediately on the horizon, Mangold has time to decide what story and, more importantly, what genre he wants to explore next. "I feel lucky that I've been able to make many different kinds of movies in my career, dramas, westerns and now an action comedy. So many of the directors I admire—Sydney Pollack, Billy Wilder, Howard Hawks—took each movie and learned from it and brought those lessons to another genre. To me, one of the sad things about filmmaking today is how little directors explore before they're pigeonholed and called 'The Master of Blah Blah' by their second picture. I think that's kind of sad—there are a lot of good arguments for the way Hollywood used to be."

If moviegoers respond to the film in the way Mangold hopes, perhaps Knight and Day will become one of those arguments.