On the two-hour season premiere of "Grey's Anatomy," Meredith and Derek learn that "happily ever after" isn't easy, a military doctor who brings in a trauma patient catches Cristina's eye, and the Chief and his staff reel at the news that Seattle Grace is no longer nationally ranked as a top-tier teaching hospital.

Plumbing leak becomes a deluge and wreaks havoc at Seattle Grace, as the Chief attempts to implement new teaching policies and George tries to retake his residency exam; meanwhile Derek hopes to move the roommates out of Meredith's house, to their surprise.