A haunting voiceover reading e-mails from Edward Snowden takes over the teaser trailer for the Snowden documentary, Citizenfour.

The movie shows a firsthand look at filmmaker Laura Poitras and journalist Glenn Greenwald’s first contact with Snowden in Hong Kong, as he became a fugitive after exposing confidential documents by the National Security Administration (NSA). Directed by Poitras, the trailer showcases how Poitras started receiving e-mails from Snowden under the pseudonym “Citizen Four,” who was seeking to expose the surveillance programs run by the NSA. What ensued was unprecedented, face-to-face access to Snowden as he remained on the run from the authorities.

Citizenfour will be released theatrically on Oct. 24.