We all knew it was coming...we just weren't sure when, and now, it is official: Thatcher Grey (the possibly slightly insane father of both the Greys, Meredith and Lexie) is returning to the world of Seattle Grace on November 8th, during episode 407 Physical Attraction... Chemical Reaction. Don't look for any clues in the episode's press release, because there aren't any besides the fact that it says Thatcher returns, but it is sure to be a really interesting episode. Physical Attraction... Chemical Reaction was written by Joan Rater & Tony Phelan ("Deterioration of the Fight or Flight Response," "Didn't We Almost Have It All?").