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.
Part 1 of a Grey’s Anatomy/Private Practice crossover. Mark flies Addison (Kate Walsh) 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.
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, his "daughter". Thatcher Grey questions the Chief’s recent behavior as Meredith comes to his defense. Cristina suspects that there is/was something going on between Owen and Teddy.
When Owen recruits his fellow Iraqi War vet, Dr. Teddy Altman (Kim Raver), 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 (Joel Grey) seeking treatment for his dementia, and the stress of Richard’s responsibilities, post-merger, are taking their toll.
Arizona is stunned when one of her patient’s parents has a much too generous donation of twenty-five million dollars to spare, but when her patient’s condition worsens, all eyes are on Arizona to fix it. Cristina is tired of Owen and begins to test her boundaries with him by ignoring in in the OR when he told her to put down the scalpel because she was doing an unauthorised procedure, and one of the Mercy Wester’s- Jackson Avery kisses her, but she ends it saying "I’m involved". Alex is losing it with the disappearance of Izzie, not to mention the left-over hos
Derek must help the unlikeliest of all; the hospital lab-tech, Isaac, when it turns out that he has an inoperable tumor surrounding his spine. Derek is juggling two things at once when he questions Richard’s authority.
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 Seattle Grace residents defend their actions in an effort to save their jobs. April Kepner (Sarah Drew) is fired.
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 father visits with a priest to attempt to convince her to renounce her homosexuality; Izzie experiences the brunt of the new surgical competition; and an accident derails a patient’s upcoming kidney donation, with Dr. Bailey promising to set things right, segueing into a crossover with Private Practice. Izzie is fired and leaves a Dear John letter for Alex and disappears.
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 with tumors, as Mark, annoyed with Cristina’s competitive zeal, tricks her into assisting on an unusual surgery.
Bailey and Alex’s patient is complicated when her schizophrenic son arrives. The residents and interns of Seattle Grace compete to survive the budget cuts.
