The Dark Knight star reveals he has spent the summer working on developing the story for the mystery film, which he is pulling triple duty on.

"I'm trying to direct a movie... so I've been writing it, acting and directing it," he explained on U.S. morning show Live! With Kelly.

Eckhart didn't offer up any further information about the movie, but he is also juggling his directorial debut with penning another film based on his mum Mary's "cowboy" upbringing.

He said, "I'm writing a western right now about my mother's life. My mother grew up in Montana. She grew up with no running water, no electricity, she rode bareback horse. They used to go out in the winter and cut ice... store it under the hay for the summer so they could go and make ice cream in the summer. She was a homesteader... They literally are the closest thing you can think of to a cowboy."

However, he plans to shake up his version of her quiet home life, adding, "I'm gonna put some drama in it."

And the 48-year-old has plenty of source material to draw from: "My mother wrote her autobiography, her memoirs, and I'm reading these and it's just heartbreaking so I decided to write a western about it."