Maggie and Meredith disagree with Derek about the best way to approach a patient’s case, which leads to a bigger argument between the couple. Meanwhile Callie feels responsible when one of her veterans is pushed too far and one doctor’s routine procedure results in a devastating diagnosis on the winter finale of “Grey’s Anatomy,” THURSDAY, NOVEMBER 20 (8:00-9:00 p.m., ET) on the ABC Television Network. “Grey’s Anatomy” stars Ellen Pompeo as Meredith Grey, Patrick Dempsey as Derek Shepherd, Justin Chambers as Alex Karev, Chandra Wilson as Miranda Bailey, James Pickens, Jr. as Richard Webber, Sara Ramirez as Callie Torres, Kevin McKidd as Owen Hunt, Jessica Capshaw as Arizona Robbins, Jesse Williams as Jackson Avery, Sarah Drew as April Kepner, Caterina Scorsone as Amelia Shepherd, Camilla Luddington as Jo Wilson, and Jerrika Hinton as Stephanie Edwards. Guest cast TBA. “Risk” was written by William Harper and directed by Rob Corn.