Season Five of Grey's Anatomy has stayed relatively drama-free - at least on the MerDer front. Well, according to guest star Eric Stoltz, who begins a three-episode stint Thursday as a serial killer admitted to Seattle Grace, that's about to change - and he's the reason for it.

His character, William Dunn, promises to shake things up for MerDer- but how? Follow the link to find out what Stoltz says goes down, along with other Grey's Anatomy spoilers!

Steve Marsi is the Managing Editor of TV Fanatic. Follow him on Google+ or email him here.