When Isaac, the hospital lab tech, has an inoperable tumor wrapped around his spine, he turns to Dr. Derek Shepherd to do the impossible, and Derek tests the Chief's authority when Richard objects to moving forward with the risky surgery.

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.