The episode begins with a dream of Izzie, Cristina, and George in the shower together. It's George's dream. Meredith refuses to go to work. She has this feeling that she will die. George and Izzie can't get her out of bed, they have to call in Cristina. Once at the hospital, the premonition seems to have some validity. A trauma victim is brought in by a paramedic with her hand still stuck inside him to stop the bleeding. As Alex soon discovers though, her hand isn't the only thing inside of him after trying to make a homemade bazooka, he's also got a piece of unexploded munitions inside of him. This places the hospital on Code Black, which essentially shuts down the surgical wing save for the one operation that has already begun: Derek and Cristina operating on the brain of a man who happens to be Bailey's husband.
Bailey's husband got into a car accident trying to get to the hospital on time because Bailey is now going into labor. Though the bomb squad, lead by Dylan Young, wants to clear out the ORs of all unnecessary personnel, Derek, Cristina, and Meredith all insist on staying (Meredith is with the paramedic, Hannah, who's got her hand in the patient). After a chat with George about being "doers versus watchers" (they feel Cristina and Meredith are the "doers"), Izzie decides to ignite things with Alex in the supply closet. Richard is trying his best to keep the hospital in some sort of order amidst the chaos, but he's having a tough time. In fact, things degrade quite quickly all around, most notably when an anesthesiologist leaves Hannah alone with the patient and the bomb while all the other doctors are strategizing with Dylan. Meredith finds Hannah having a nervous breakdown, about the pull her hand out and potentially put them all in danger (not to mention kill the patient who's bleeding she's suppressing). Hannah does pull her hand out and run away but not before Meredith can take her place as the girl with her hand in the explosive patient.