Luc Besson needs actor bond

Luc Besson only casts an actor who he can relate to.

The French director helms the action sci-fi movie Lucy, starring Scarlett Johansson in the title role. Her alter ego is a student studying in China who gets roped into trafficking a new drug, which leaks into her body and increases her brain function, turning her into a super-human.

When auditioning for the part Luc was certain he'd found the right person for the role after witnessing the actress' curiosity.

"If you're going to spend eight months with someone, you need to be sure about them. Do I like you? Do you like me? Are you interested in the movie?" he explained to British magazine TimeOut London.

"When Scarlett came in she asked a thousand questions... [Her] character in Lucy is about vulnerability. Something extraordinary is going to happen to her, so I take the worst case scenario: an American in Taiwan, 15,000 kilometres from home. She doesn't speak the language. She's an average woman."

The movie co-stars Morgan Freeman as Professor Norman, who is looking into the concept of humans using more than ten percent of their brain at the same time Lucy's knowledge is expanding. There is one scene in the film which has the audience on the edge of their seats - a sequence which Luc was excited about ahead of filming.

"I start with a key shot. When I wrote the car chase in Lucy, I knew where it would happen: Rue du Louvre in Pairs, backwards, at noon!" he laughed. "I went along there, took a look at the angles we could shoot, where the cars could go, and put it together that way."