Filmmaker Laura Poitras talks to CBC News about her film Citizenfour and the process of working with whistleblower Edward Snowden, a former intelligence analyst who leaked documents detailing the NSA's domestic spying program.

Poitras tells CBC's Amanda Lang about Snowden's initial — anonymous — approach, the decision to meet him and the process behind her Oscar-nominated documentary.

"People talk about the film sometimes and they describe it as sort of a bit of a mystery," Poitras says. "And that’s what it felt like."

Click the video above to see the full interview.