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 between Teddy, Cristina and Owen in the aftermath of Cristina's startling confession.

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 surgery, and Derek's suspicions are raised when the Chief recruits Meredith to assist with a high profile operation on.

As Thanksgiving, Christmas and New Year's pass, Miranda is visited by her father, William, who disapproves of her choices in life; meanwhile, Mark and Lexie must cope with the shocking arrival of a woman from his past, and Thatcher Grey questions the Chief's recent behavior as Meredith comes to his defense.

When Owen recruits his fellow Iraqi War vet, Dr. Teddy Altman, as the new cardiothoracic surgeon, Cristina questions Teddy's abilities in the OR and the nature of their past relationship. Meanwhile Izzie returns to Seattle Grace with her high school mentor seeking treatment for his dementia, and the stress of Richard's responsibilities, post-merger, are taking their toll.

A generous donation is offered to Seattle Grace by the parents of Arizona's 10-year-old patient. however, when his condition worsens, she finds herself in a conflict of interests. Meanwhile, Cristina tests her boundaries with Owen at the hospital, and adding insult to injury, Alex is left with all of Izzie's hospital bills to contend with.