I think it is the hardest thing in the world. I'm endlessly intrigued by what human nature is capable of, both the horrible things we are capable of and also the heroic things. I'm really interested in exploring that side of human nature.

It's the open ocean right now because it's so unique. It's a really unique way of doing American television. There are a million possibilities. We can stay with the cops. We can introduce new worlds. And, who knows where it will end.

I am endlessly fascinated by this notion that everyone has a secret. Some of our secrets are tiny, small things, and some of them are huge. Given that reality of the human condition, that's what our characters will go through. There will be some things where you'll just be like, "What the hell! How the hell did that happen?"

But, for the role of Sarah Linden, we saw everybody. Everybody wanted this role. Every female actor in town really wanted to play a real woman and be in this drama. It was incredible that all these women were coming in. And then, Mireille [Enos] walked in the door and she was reading the lines that I had written, and I saw her in that field. I was like, "Wow, she's the one."

Before I write anything, before I create any assumption in my mind about what it's like to be in that world, I go out there first. I'm very drawn to darkness and light, very drawn to cop drama, because there are very few places besides war and murder and a homicide investigation where you see the extremes of human nature - the darkest crevices and cracks in what people do to one another.

It was a very, very intense and long casting process [for The Killing] because we really had to find the right people who could carry the weight of this story, who had the chops and who had the spirit, where they could bring in so much of their own selves to these characters. So, the casting process took many months.

The thing I love about this story [The Killing] and this type of storytelling is that I don't have to know the end before I know the beginning.