"Homeland" actor Rupert Friend: Peter Quinn the show's "moral compass"

"Homeland"'s season four finale airs Sunday night, and the show's nearly six million weekly viewers are expecting a dramatic end.

In the latest season, Carrie Mathison, played by Claire Danes, is the CIA station chief at the U.S. Embassy in Islamabad, Pakistan. As she continues to fight the global war on terror, her relationship with operative Peter Quinn, played by Rupert Friend, is put to the test.

Although Friend wasn't initially cast to appear in more than an episode, the writers quickly wove him in after an impressive performance on set.

"I was supposed to do one scene, and then it was relocated to North Carolina, and you don't know what you're doing," Friend said Friday on "CBS This Morning." "Then I eventually found out you're going to kill (Damian Lewis' character Nicholas) Brody, and then I wasn't, and then I was back, and now I'm back again."

Relatively unknown to American audiences before the Showtime drama, Friend trained at the Webber Douglas Academy of Dramatic Art in London, and his first professional role was opposite Johnny Depp and John Malkovich in "The Libertine."

Now, as somewhat of the fiber holding Carrie and many of her operations together, Friend has found his calling as the black-ops agent.

"I think Quinn in many ways is kind of the moral compass of the show, which is a strange thing to say about someone who kills people for a living," Friend said. "I think when you've lived a life that dark and started to question it, you're oddly perhaps more uniquely placed to sit in some kind of judgment over the actions of what everyone else is doing."

For many, the complex drama is even more compelling because of its parallels to current events. Friend said those similarities are purely by chance.

"I think it's occasionally incredibly coincidental how there will be events in life that echo the things that we've just been playing out," Friend said. "I don't think it's in any way reflective of them."