Grey's Anatomy Season 5, Episode 17 I Will Follow You Into the Dark Drama IMDB 8.226 Country United States Duration 43 min Air Date 2009-03-12 Actors Ellen Pompeo (Meredith Grey) James Pickens Jr. (Richard Webber) Chandra Wilson (Miranda Bailey) Kevin McKidd (Owen Hunt) Camilla Luddington (Jo Wilson) Kim Raver (Teddy Altman) Chris Carmack (Atticus Lincoln) Jake Borelli (Levi Schmitt) Anthony Hill (Winston Ndugu) Caterina Scorsone (Amelia Shepherd) Overview Derek decides to quit after learning that more of his patients have died than survived; Izzie's interns make an unsettling discovery about "Patient X."