The staff tries to deal with trauma in the wake of the deadly rampage.
Meredith finally tells Derek about her pregnancy and miscarriage; Cristina experiences PTSD.
Issues surface when Derek's estranged sister, Amelia, visits unexpectedly.
Derek and Meredith visit the obstetrician and receive disturbing news.
As part of their training, Seattle Grace's residents are put in charge; the attending surgeons compete for a million-dollar grant.
A film crew visits the hospital six months after the shooting to document the road to recovery.
Owen puts the residents through a rigorous trauma certification drill.
A team of doctors tries to save the life of a political figure from the Middle East.
Derek and the attendings go out to celebrate when he gets the grant he needs for his clinical trial.
Derek takes Cristina on a fishing trip; Teddy directs her compassion toward a dying patient.
A gunman opens fire at a local college, sending mass casualties to the hospital; Arizona's return is not warmly received.
Arizona tries to reconcile with Callie, who has big news to share; the residents receive new interns; the Chief makes an announcement.
Meredith feels left out when Derek breaks ground on his clinical trial; Bailey's new idea does not go over well with the Chief.
Meredith and Lexie's father returns to Seattle Grace with stomach pains and a new girlfriend; Alex butts heads with the new OB.
Meredith volunteers to run the ER for a night in hope of proving that she is chief-resident material; Bailey and Eli get into mischief.
Meredith's fertility treatments start affecting her eyesight; Mark talks to Callie and Arizona about his role as a father.
Richard tries to get Adele into Derek and Meredith's Alzheimer's trial; Arizona and Mark try to plan a baby shower for Callie.
A cataclysmic event leaves the doctors shaken; Callie, on the verge of a life-changing moment, starts imagining about the hospital and her friends.
Everyone tries to help Callie and her baby recover; the death of a trial patient impacts Derek and Meredith in different ways.
Callie and Arizona's wedding is not coming together as they hoped it would; Meredith and Derek make a life-changing decision.
Work and personal pressures leave Meredith on edge; formal interviews for the chief resident position begin; Lucy and Alex's relationship is tested.
Meredith's dishonesty is revealed, leading to unexpected consequences for her and others; the new chief resident is chosen.