Diane Lane says 'Superman: Man of Steel' will cover the superhero's life from his childhood.

The actress - who has been cast as the caped crusader's adoptive mother Martha Kent in the upcoming film - says she was locked in a room with The Script for three hours to ensure the plot remains a secret - but still revealed that Superman's origins will be covered.

She told E! Online: "I read the script under lock and key. I was locked in a room with the script and was only allowed three hours with it. I nailed it into my memory. I'm really excited.

"I'm really not allowed to talk much about it, I think, but it does cover the entire range of years, from infancy on."

The brunette beauty is set to star alongside Henry Cavill in the movie which is being directed by Zack Snyder.

Zack said of Diane's involvement: "This was a very important piece of casting for me because Martha Kent is the woman whose values helped shape the man we know as Superman."