The season follows the story of surgical interns, residents and their competent mentors, as they experience the difficulties of the competitive careers they have chosen. It is set in the surgical wing of the fictional Seattle Grace Hospital, located in Seattle, Washington. A major storyline of the season is the characters adapting to change, as their beloved co-worker Stevens departed following the breakdown of her marriage, O'Malley died in the season premiere—following his being dragged by a bus, and new cardiothoracic surgeon Teddy Altman is given employment at the hospital. Further storylines include Shepherd being promoted to chief of surgery, Seattle Grace Hospital merging with the neighboring Mercy West —introducing several new doctors, and several physicians lives being placed into danger—when a grieving deceased patient's husband embarks on a shooting spree at the hospital, seeking revenge for his wife's death.
The hospital staff is left to deal with the aftermath of George's passing. Hitting the staff hard, they all find unique ways to get through the various stages of grief. George's mo...
Everyone is struggling after losing one of their own and are turning to any distraction they can find. Meredith and Derek seem to be consummating their marriage anywhere and everyw...
Several weeks after her near-death experience, a recovering Izzie returns to work. Meanwhile, nervous that there will be layoffs in the hospital in the wake of an announcement from...
When Meredith and Lexie's father, Thatcher, returns to the hospital with a failed liver, it's up to Meredith to save his life. Meanwhile, Izzie empathizes with a patient riddled wi...
The residents of Seattle Grace and Mercy West vie for surgeries and their careers as day one of the hospital merger begins. Meanwhile, Arizona stands by an enraged Callie when her ...
After a burn victim unexpectedly dies in the midst of a chaotic ER, the Chief and board member Jennings interrogate the residents to find the culprit, as all the Mercy West and Sea...
When Isaac has an inoperable tumor wrapped around his spine, he wants Derek to do the impossible. Derek tests the Chief's authority when Richard objects to moving forward with the ...
A generous 25 million donation is offered to Seattle Grace by the parents of Arizonas 10-year-old patient, she finds herself in a conflict of interest when his condition worsens. C...
Owen recruits Dr. Teddy Altman, a former Iraqi veteran, as the new cardiothoracic surgeon. Cristina questions her abilities in the E.R. and relationship with Owen. Izzie returns ...
As Thanksgiving, Christmas and New Year's pass, Miranda gets a visit from her father, William who disapproves of her choices in life. Mark and Lexie cope with an arrival of a woman...
Mark flies Addison to Seattle to help with a difficult procedure on his pregnant daughter, Sloan, Owen questions Teddy's motives when she assigns Cristina the lead on a complicated...
After learning of Richard's drinking problem, Derek confronts him for the sake of his friend and the hospital, Izzie returns, hoping to reconcile with Alex, and tensions run high b...
As Derek begins his role as interim chief, he faces a potential lawsuit when Bailey and Meredith's patient awakens from anesthesia mid-surgery. Meanwhile, Teddy refuses to place Cr...
It's Valentine's Day, and the doctors must treat dozens of injured people after the roof collapses at a popular romantic restaurant; Derek tries to manage his busy schedule as Chie...
In his new role as Chief, Derek restores the hospital lecture series, and Richard, Bailey and Callie present to the group pivotal surgical cases from their pasts Bailey reflects on...
When famous surgeon Dr. Harper Avery is rushed to Seattle Grace-Mercy West, the staff is surprised to discover that one of their own is related to this legend, and his unorthodox r...
A patient who needs an extremely difficult surgery comes to Seattle Grace, and it's Richard and Owen who vie for the opportunity to tackle it. But the decision lies in the hands of...
When Teddy's patient seeks to end treatment and her life, she turns to Hunt for help. The situation triggers Hunt's memories of his life at war and his past relationship with Teddy...
When Alex's younger brother, Aaron, shows up at Seattle Grace-Mercy West with a hernia, it's up to Alex to get Bailey's approval for his pro bono surgery. Matters are further compl...
Sloan returns to Mark's apartment, just as she's going into labor, and Teddy, Mark and the still-fighting Callie and Arizona are there to help with the birth and to get Mark throug...
Bailey preps the team with mandatory sensitivity training prior to admitting a 700-pound patient with compounded medical issues, and the case proves to be challenging in every sens...
An elderly patient admitted into the E.R. for a heart condition sees a familiar face, a long lost love who happens to be in the E.R. as well for a fractured arm, and the staff find...
Seattle Grace Hospital is hit with a crisis like no other in its' history.
Cristina and Meredith's surgical skills are put to the ultimate test.