- Ellen Pompeo (Meredith Grey)
- Chandra Wilson (Miranda Bailey)
- James Pickens Jr. (Richard Webber)
- Caterina Scorsone (Amelia Shepherd)
- Camilla Luddington (Jo Wilson)
- Kevin McKidd (Owen Hunt)
- Kim Raver (Teddy Altman)
- Jason George (Ben Warren)
- Chris Carmack (Atticus Lincoln)
- Anthony Hill (Winston Ndugu)
- Adelaide Kane (Jules Millin)
- Alexis Floyd (Simone Griffith)
- Niko Terho (Lucas Adams)
- Harry Shum Jr. (Benson 'Blue' Kwan)
- Trevor Jackson (Wes Bryant)
Grey's Anatomy — S5E17
Episode: I Will Follow You Into the Dark
Air Date: 2009-03-12
Runtime: 43 min
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."