Watch Grey's Anatomy Season 11 Episode 16 to see what happens when Meredith asks Callie, Alex, and Maggie if they think Derek is cheating on her. She worries that since he did it with her, that he'll do it again. Derek makes a surprising return home in order to explain himself! Meanwhile, Arizona sees Callie on a date, but wants to warn her about the woman she saw Callie kiss. Maggie reveals to Richard that she knows about her Alzheimer's gene. Jo gets overly emotional when they are unable to save a pregnant woman, but are able to save the baby.