Sony Pictures Releasing launched an on-line game today that will give audiences a unique look into the storyline of the contemporary action thriller Salt, which stars Angelina Jolie.

The Day X Exists game combines video based story telling with espionage-themed missions and asks users to delve into the world of Agent Evelyn Salt after she is accused of being a sleeper spy within the CIA. Players are recruited by Salt to stop a mysterious plot called 'Day X' and clear her name.

"This is about participation and rewards we can give - if you play, you might learn something about Salt that you won't get from just seeing the film," said Nathan Mayfield co-founder of Hoodlum, a Brisbane based company that designed and produced Day X Exists for Columbia Pictures.

Nine missions will be released across a four-week period with the first mission activated on Tuesday July 27. Upon the completion of the final mission, users can enter a sweepstakes to win Sony Electronic prizes valued at $12,000.

Directed by Phillip Noyce, Salt tells the story of Evelyn Salt (Jolie), a CIA officer who swore an oath to duty, honour and country and goes on the run when a defector accuses her of being a sleeper spy.

The film opened in the US over the weekend to a huge $US 36.5 million dollars.