Facing the impossible choice of which dying newborn twin to save, Alex is ready to cede the weighty decision to Bailey. But Arizona won't let him. She tells Alex how in awe she's been since he stepped up and volunteered to shoulder that burden for the twins' parents. "If you give it to Bailey, you won't be able to look at yourself in the mirror, I promise you. You'll always wonder what kind of doctor you COULD be," she tells him. Watch this scene from Season 12, Episode 3, "I Choose You," and don't miss Grey's Anatomy THURSDAYS 8|7c on ABC.