The Crazy, Stupid, Love actress was speaking to My Entertainment World when she was asked about her role in the upcoming Christopher Nolan film.
She said: "I play young Talia al Ghul. I can't give too much away because I promised Mr Nolan I wouldn't say anything. There are too many secrets about the character and the movie."
Fans have been speculating about Marion Cotillard's character Miranda Tate, believing her to also be Talia al Ghul.
Meanwhile, King stated that she loved shooting The Dark Knight Rises.
She commented: "It was so cool - I had an amazing time. I got to travel to places I'd never been to before. Christopher Nolan is so nice. So is Christian Bale. I just had the best time."
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Watch the Dark Knight Rises trailer below: