The suspense thriller I Am Number Four, adapted from the YA book of the same name, tells the story of nine members of an alien race, each with their own talents and legacy, who are being hunted on Earth by ruthless enemies sent to destroy them, one by one. The next one in line is Number Four, John Smith (Alex Pettyfer), the new kid in a small Ohio town, where he unexpectedly meets his first love, Sarah (Dianna Agron), and a curious teenager named Sam (Callan McAuliffe). As he discovers his powerful new abilities and a connection to the others who share his destiny, John must decide how much he is willing to sacrifice to meet his true potential.

The screenwriting team of Al Gough and Miles Millar were first hired to write the script for I Am Number Four while the manuscript was still in its first draft. In this exclusive interview with Collider, they talked about how they were intrigued by the project from the moment they heard about it, the collaborative process between them and the author, the changes that they needed to make and the things that they wanted to keep the same, and how they left the story open for possible sequels, as it was sold as a four-book series. They also talked about their process of writing together, and how they never like to focus on just one project at a time. Check out what they had to say after the jump:

Question: How did you originally come to I Am Number Four?

AL GOUGH: We came on, initially, right after DreamWorks had bought the manuscript, so that was in July of ‘09.

MILES MILLAR: There was an article on the front page of Variety and Al came in and said, “This sounds really intriguing. Let’s hope they call us.” And, I think it was three days later when we actually got a call about it and they sent us the book.

GOUGH: They literally sold the first draft of the manuscript of the book. Even the development of the book was in the early stages. It was like the book and the movie were being developed, at the same time. So, we had done quite an extensive treatment. When you’re adapting a book to a movie, things change and you need to collapse timelines, look at characters, and see what stands out and what’s important.

Was it easier to adapt a book that people hadn’t read yet because it was in such an early stage?

MILLAR: Often these Young Adult books, like Twilight or Harry Potter, become set in stone. You really can’t change much from the original. I think people would be up in arms, if you changed anything from Twilight. You have to follow the letter of the law, in terms of what is written by the authors. Here, it was much more at a stage where James [Frey] was very open to hearing thoughts about making the novel more streamlined and making the characters feel more unique. For us, that was very beneficial to have his support in that, and obviously his ideas as well. It was very much an interaction between the author and us.

GOUGH: That was very unique, in terms of these YA adaptations. Then, we got the sign off to write on Labor Day and had the first draft in by Halloween. We got notes and had the second draft by Thanksgiving, and that’s the one that Mr. Spielberg read. And then, we got his notes and had to turn that draft around by Christmas, and then worked through the holidays on it as well. Then, it got D.J. Caruso attached and was greenlit.

MILLAR: For the number of drafts and the speed of turn-around from the studio, it was the most intensive we’ve ever experienced, in terms of the incredible energy and the momentum the project had. It was probably the fastest turn-around from inception through the movie.

GOUGH: From the time they bought the book to the time they started shooting the movie, it was nine or ten months.

Were there things that you knew you would have to change, in order to make it work as a film?

GOUGH: The first thing was aging the characters up, ‘cause they’re younger in the books. I think John is 14 and Sarah is 16, in the book. And also, we had to compress the timeline. In the book, it happens over the course of eight or nine months, but that had to move faster. And then, it was giving the Mogodorians a commander, so that there was somebody who was in charge. We had to visualize the Mogodorians. In the book, there were a lot more of them. There was almost an army of them, but we wanted the idea that it was an elite squad of them. That way, they felt like they were a threat, but it didn’t feel like they were going to have to go around in a personnel carrier.

MILLAR: Also, we had to work on the love triangle in the story and make sure that felt unique and worthy of a story. We wanted to get audiences involved with the story of the characters and the story of their relationship.

How did that relationship evolve from what it first was in the initial manuscript?

GOUGH: That’s one thing we had learned from our Smallville experience. In the initial draft of the book, Sarah was a cheerleader who was dating Mark, who was the quarterback of the football team. Mark was obviously not a good guy, and yet the female love interest was dating this guy, so you’d go, “Why is she dating this guy? Doesn’t she see what everybody else sees? He’s kind of a jerk.” It was the idea that, when John first comes to town, she was dating Mark, but she’s broken up with Mark. And, Mark is resentful and still wants her back, more because it’s the prize that he can’t have, but she’s moved on. You like her more for recognizing that she was with this guy, and it’s a small town, but at a certain point, they grew apart and this isn’t the guy for her. We had to change that relationship stuff.

MILLAR: The other thing we added, in terms of her character, was giving her something to do. That’s where the idea of photography came from. That wasn’t in the initial draft of the book, but we wanted to give her some personality.

GOUGH: It’s something visual that she does, so it seemed like a way for her to express herself and her view of the world and the idea that, even though she lives in this small town, now she feels like an outsider as well. It made her and John more kindred spirits.

In reading the book, was there anything that you really wanted to be sure to keep for the film?

MILLAR: The great thing that the book did have, which was rare, was all the main set pieces. The Halloween hayride was there, which was a great set piece. The events of the finale were at a cabin, and we changed that to the high school. James [Frey] has done an incredible job of actually giving this story architecture. It really felt that there were incidents in the book, which is rare. There was very unique action.

GOUGH: It was nice, in that the bones were all there in the book. It wasn’t like you had to do a radical reshuffling of things. It was more about compression. And then, once you honed in on those action set pieces, what you got out of those set pieces, in terms of character development. Initially, Sam didn’t witness John’s powers in the hayride because, in the book, there was a lot more time and there was another thing where he witnessed John’s powers. Some of that stuff was just about compression of time to keep the thriller aspect of the story strong and moving forward.

How do you keep writing for high schoolers fresh?

GOUGH: Part of it is always trying to not do the same scenes that we’ve written 100 times. That’s good ‘cause it actually forces you to think about it. Obviously, each situation, whatever the story is, is different as well. The high school experience and the emotional scars are so universal that we can all plug into that, no matter what era we went to high school in.

Was there ever a version of the script that showed the alien planet?

GOUGH: In early drafts, there were definitely flashbacks to Lorien, but at a certain point, it’s about how much of the information you need.

MILLAR: It also becomes about budget. To do those scenes justice, it would be on a massive scale.

How much of the action sequences were written out in the script?

GOUGH: They were completely written out. Action sequences are like musical numbers. They need a concept, they need to be plot-movers and show-stoppers ‘cause you want people to remember them, and you have to move the character and the story along. So, the Haunted Hayride is John and Sarah really getting together, and Mark getting between them. It’s Sarah’s final, “We’re done.” After that, she kisses John for the first time and it pushes that story along. And, John’s powers are revealed to Sam in the woods, so it pushes that story along. You want to make sure that you have that kind of momentum, coming out of an action sequence, where it forwards the plot and the character.

Had you also been asked to leave this a bit open for a sequel?

GOUGH: It was sold as a four book series. The end of the movie is basically the end of the book, where they go off to find the others. You feel like the movie has a satisfying ending, but the Mogodorians are still out there and the other six are still out there. The idea was to blow up the Death Star, but not take down the Empire. There’s still stories to tell, in success, if people want another movie. There is actually more of the story to tell.

As writers, what is it like to hear the actors bring your words to life?

GOUGH: When the right actors do it, it’s fantastic. During the casting process, when you hear all the people that aren’t the right actors, it is so painful.

MILLAR: It’s painful and torturous.

GOUGH: And then, when the right people read it, you’re literally like, “Oh, okay, thank god! That’s the way it’s supposed to sound.” You stop doubting yourself.

MILLAR: It is the weirdest thing. As producers, when an actor comes into the room to audition, you want them to do amazingly well, so that the process can end. It can just be sofrustrating when you don’t hear the words the right way. Then, you second-guess the scene and it’s just a horrible process. It’s all about the end and finding the right people. However unfortunate the process is, it’s about getting the right people. But, it’s indescribable, how painful it can be.

What is your writing process when you’re working together?

GOUGH: We’ve written the same way, since we started writing together 16 years ago. We’re in the same room, and I write on legal pads and Miles writes on the computer, but we break the stories and we write all the scenes together. That’s how it’s done. It’s like any long-term partnership. It’s a marriage. But, especially in this business, it’s nice to have somebody to go through the ups and the downs with together.

Are you solely focused on Charlie’s Angels now, or are you also working on developing other projects as well?

MILLAR: We never focus on one thing at a time. Charlie’s Angels is our main focus, at this moment, but we’re working on a movie for Universal, called Monster High.

GOUGH: We have probably a dozen projects that we’re producing.

MILLAR: We’re looking at one project to direct. For us, it’s always about keeping as many balls in the air as we can, and never taking anything for granted.