A blood-curdling trailer was released on Wednesday from a new British film about the Iraq War. In the thriller Official Secrets, Keira Knightley plays a whistleblower from the British secret service who leaked information to The Observer.

The story is based on truth. In 2003, 29-year-old Katherine Gun, who worked as a translator for the secret service, leaked secret information about illegal activities of the United States to The Observer. Gun was confronted with an e-mail in which the United States asked for help in intercepting six countries of the United Nations that were influential in approving the Iraq war. The agent who decided to share the information was prosecuted. A year later, the authorities dropped the case against her.

Keira Knightley plays the role of Katherine. Her opponent is Matt Smith, who plays The Observer journalist. Official Secrets will be released in the United Kingdom on October 18.