In his new role as Chief, Derek restores the hospital lecture series, and Richard, Bailey and Callie present to the group pivotal surgical cases from their pasts Bailey reflects on her first days as a shy resident, Callie looks back on a polio case, and Richard recalls a case in which he and Ellis worked on a patient diagnosed with GRID, a virus later called AIDS.

It's Valentine's Day, and the doctors must treat dozens of injured people after the roof collapses at a popular romantic restaurant; Derek tries to manage his busy schedule as Chief of Surgery; Meredith wrestles with her new duties as the Chief's wife; and Mark and Callie team up to convince Sloan to do the right thing for her baby.

After being named interim chief, Derek begins to settle into his new position but faces a lawsuit when Bailey and Meredith's patient wakes up during surgery. Meanwhile, Teddy refuses to let Cristina be a part of her service, Alex continues to work with Arizona in pediatrics, and Mark avoids talking to Lexie who is still heartbroken over their break up.