"Fear (Of The Unknown)'" is the twenty-fourth episode of the tenth season of Grey's Anatomy and the 220th produced episode of the series. It is also the 331st produced episode of the Grey's Anatomy franchise. It was broadcast on May 15, 2014.
The day arrives for Cristina to leave Grey Sloan Memorial Hospital but, as she continues to put off her departure, a possible act of terrorism rocks Seattle sending an influx of victims to the E.R. As Cristina struggles to take a step towards her new future in Zurich, she finds herself unable to find closure with both Owen and Meredith while Meredith grapples with her future as she and Derek find themselves on the brink of a life-altering decision, as Amelia seizes the opportunity to take control of Derek's neuro service. Meanwhile, as the doctor's wait to learn whether they are dealing with an act of terrorism, April questions her ability to raise her and Jackson's child in an uncertain world while Leah and Shane both find themselves dealing with drastic career changes. Callie and Arizona both try to cope with giving up on their attempt to have a second child. Meanwhile, Cristina's departure unknowingly sends Alex and Bailey on a collision course and Cristina's replacement, Maggie Pierce, has a profound effect on one of the doctors.
- "He doesn't know that, he's an idiot. For all he knows it could be the worst day of his life. You know how people say 'who knows, I could get hit by a bus tomorrow', that seems pretty far-fetched. Until you have a friend who's hit by a bus. The point is you never know what kind of day is coming"
- "Whenever we think we know the future, even for a second, it changes. Sometimes the future changes quickly and completely and we're left only with the choice of what to do next. We can choose to be afraid, to stand there trembling, not moving, assuming the worst that can happen. Or we step forward into the unknown and assume it will be brilliant."
- "Portions For Foxes" - Caught A Ghost
- "Take Me Home" - Aqualung
- "Ruby Blue" - Sleeping At Last
- "Where Does The Good Go" - Tegan & Sara
- "99 Red Balloons" - Sleeping At Last
This episode's title originated from the song Fear (Of The Unknown), originally sung by Siouxsie and the Banshees.
- Cristina narrates the voiceover for episode.
- This is the last episode to credit Sandra Oh, Gaius Charles and Tessa Ferrer in a starring capacity.