You may know him from The Americans, but actor Matthew Rhys is a whistleblower in Steven Spielberg's The Post. Rhys plays the whistleblower who leaked the infamous Pentagon Papers.

"I'm very fortunate to be able to play the incredible individual Daniel Ellsberg. He was a former Marine and Pentagon employee who, in the late 60s, who was sent to Vietnam for some time to help compile a report for Robert McNamara about how America was doing," explains Rhys. "What he witnessed repelled him so much that he leaked the report in order to try and bring about an end to the war."

Ellsberg is not nearly as wellknown in pop culture as the other key characters in the film, such as the Washington Post publisher at the time Katharine Graham (played by Meryl Streep) and distinguished editor Ben Bradlee (played by Tom Hanks).

On arriving to the movie set the first day to work with Spielberg, Streep and Hanks, the British actor says he was terrified!

"When the reality of it strikes, you go, 'Oh my gosh! I'm going to actually have to do it now!" Rhys calls Spielberg a boyhood hero and says when the director yelled action, " was terrifying and exhilarating."

But Rhys survived, and soared, alongside his all-star cast of Hollywood heavyweights. The Post opens in theaters everywhere Friday, January 13.

Markette Sheppard is host of Great Day Washington and your resident "Mom at the Movies." She is also a wife, mother of a rambunctious 4-year-old and avid film lover. You can see more of her movie previews and reviews weekdays at 9 am.