Diane Lane, who plays Martha Kent in the new "Superman" movie reboot, says she "had to read the script under lock and key in a room."
The new "Superman" film, "Superman: Man of Steel," stars Henry Cavill, a 27-year-old British actor who stars in the Showtime series "The Tudors," as the superhero and is set for release in December 2012.
"I'm not allowed to talk about it," Lane, 46, said on "The Tonight Show with Jay Leno" on Wednesday, April 13. "It's top secret. I had to read the script under lock and key in a room. You go to the offices and it's a locked door and the curtains are drawn and that was the time I had."
Kent and her husband Jonathan, played by Kevin Costner, are Superman's adoptive human parents.
Lane, the wife of actor Josh Brolin, recently appeared in the movie "Secretariat" and is also known for her roles in the films "The Perfect Storm" in 2000 and "Unfaithful" in 2002, the latter of which earned her an Oscar nomination.
She also recently filmed the movie "Cinema Verite" with Tim Robbins and James Gandolfini. The film, which comes out on April 23, tells of the first American family who are picked as subjects of a reality television show. Lane said she gets "a little depressed" when she watches reality TV herself.
Christopher Nolan and David S. Goyer, the writing team behind "Batman Begins" and "The Dark Knight," are penning the script for the new film and Nolan, who also directed both "Batman" films, is also on board as a producer.
Earlier this week, it was announced that Michael Shannon of the HBO series "Boardwalk Empire" will play the villain General Zod in "Superman: Man of Steel." Amy Adams is set to portray Superman's love interest Lois Lane.
Others who have played Martha Kent on screen include Annette O'Toole, who stars in the CW series "Smallvillle" and K Callan, who appeared on the 1990s show "Lois & Clark: The Adventures of Superman" and Phyllis Thaxter, who played the character in the 1978 movie "Superman," which starred Christopher Reeve.
Eva Marie Saint played Martha Kent in the 2006 film "Superman Returns," which starred Brandon Routh as the superhero.
Check out a clip of Diane Lane discussing "Superman: Man of Steel" on "The Tonight Show with Jay Leno" on Wednesday, April 13.