While director Tod Williams and his fellow "Paranormal Activity 2" creative forces were busy all summer shooting the follow-up to one of 2009's breakout hits, they were also focused on what might take place in a third installment of the horror franchise. (Beware of spoilers below.)

"You can't help but joke and think and imagine what might happen next," Williams told us. "And of course, in the making of this movie, we thought carefully about things we suggest. Because we had to work within what was suggested out of the first movie. We were married to any detail that was dropped in the first movie. We knew whatever we say in this movie has potential to grow and blossom into a whole other thing. There are a lot of good ideas of where it may go."

Now a go seems inevitable: "Paranormal Activity 2" opened to $41.5 million this weekend. While there's no word if Williams will return to the director's chair — and he demurred when pressed on this point — he did speak at length about what he and the folks behind "Paranormal Activity" view as the "soul" of the franchise.

"To me, the soul of the series is the degree to which it allows the audience to bring their creative imagination to it," Williams explained. "Movies are like a conversation. Some movies hog the conversation and some movies talk just enough and allow the audiences to fill in the blanks."

Williams went on to state two guiding principles for the franchise: "It has to feel real" and "If we had to make a choice between real and scary, we had to choose real."

"We'd rather make a boring and real movie than a scary and unreal movie," he added.

Would "Paranormal Activity 3" have to be comprised of found footage, as the first two are, or could it ever abandon that formula? "Going into a more traditional format? I think anything is possible, as long as you cleave to those first two principles. But it does seem to me that part of the DNA of the movie is this idea of found footage," Williams said.

And given the fact that "Paranormal Activity 2" was largely a prequel, does "PA 3" have to take place before the events of both films? Will the franchise continue to push backward in time, essentially telling its story in reverse?

"It could go either way," Williams teased. "Or sideways."

Check out everything we've got on "Paranormal Activity 2."

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