As Seattle is plunged into a major storm, Meredith goes into labour. When the hospital loses power, her doctor and all the others are forced to work in the dark. Cristina must perform surgery in almost complete darkness while Arizona, Alex, and Lauren must ward off terrified parents. Then, just outside the hospital, a school bus full of people crashes and flips over, forcing several doctors to rescue its passengers. Cristina finally confronts Owen on his desire to have kids.