Remember when we said that you'd learn more about Mellie's background on Scandal in the coming weeks? Well, when her sister arrives on the March 19 episode, lots of skeletons will come flying out of FLOTUS' closet.

"Mellie's past and where she comes from is not at all what she wants you to think. She is living her present. When her sister comes, it's a little mini Armageddon," Bellamy Young tells TVGuide.com, declining to name the mysterious guest star (Lena Dunham and True Blood's Lauren Bowles both appear in the episode). "It's not a happy reunion by any means."

Check out all this week's Mega Buzz items!

If Mellie's sis doesn't completely derail her presidential dreams, she will most definitely tear down the pristine, privileged façade Mellie has worked oh-so-hard to build over the years.

"You can tell this about people in life when you meet them. You can tell that they're working hard and you can see that sort of effort," Young teases. "That seems to come out of their own low self-esteem and then whatever perhaps difficult circumstances they grew up in. That's definitely true for Mellie. All the overarching propriety and all the judginess and all the perfect pearls is coming from somewhere, and it's fun to find out where. She did not start out where she ended up."

Crave scoop on your favorite TV shows? E-mail questions to mega_scoop@tvguide.com or drop us a line at Twitter.com/TVGuide