Can you talk about the casting process? How did Ethan Hawke, Emma Watson and David Thewlis became involved, and what did they bring to the film?
AMENABAR: In the case of Emma, it was one of those crazy ideas. We thought why not. She’s now an actress that everybody would want to work with and she’s very smart. She’s beautiful. And, of course, she had nothing to do with that atmosphere. I think she’s a great actress. Also, she understood what we wanted to do, I mean the meaning of this movie, and it was a challenge for her.
Did you allow them to go off script and try things in certain scenes?
AMENABAR: Yes. I like that. I remember some of the scenes where we would just shut down and they started suggesting things. Then, I could feel the real interaction between directing and acting, when an actor or an actress really suggests very interesting things. In the scene when Ethan and Emma are sitting in the bathroom, I remember they were playing with the order of the lines, and it worked much better.
Was there anything they brought to their performances that surprised you?
AMENABAR: In the case of Emma, she had very few elements since we know so little about her. She decided to play on credibility, meaning that with everything she said you have to believe her. That was her goal every day.