Mad Men viewers are still buzzing over last Sunday's unexpected storyline: Yes, Joan really did sleep her way into a five percent partnership and, no, Don will never know if it was his pitch, or her decision, that won the firm its Jaguar account.

How did star Christina Hendricks react to the storyline? She had a lot more time to process the circumstances than her character.

"[Series creator] Matt [Weiner] had told me about that storyline… either last season or the season before,” Hendricks tells GQ. “[He] was planning on using it before, but the development of the characters just didn’t get to that point. So I’d had some knowledge of it for quite some time."

The actress admits she was "nervous" over how others would react, but her trust in the man in charge eased her concerns.

"I think Matt's writing and the way it was done shows what people will do out of necessity and for survival. I thought it was beautifully written."

Read the full interview with Hendricks now and react: Do you understand Joan's decision?

Matt Richenthal is the Editor in Chief of TV Fanatic. Follow him on Twitter and on Google+.