Candice Afia

Meredith, Cristina, Izzie and Alex spend their first day as residents with their own interns, including George, repeating his internship after failing his exams, and Meredith's half-sister. Cristina searches for Burke, who is nowhere to be found and Richard resumes his position as chief of surgery.

Cristina and Burke's wedding day arrives - along with the interns' first exam results - and a successor to the Chief is named, as Callie and George make a big decision about their relationship.

The residents and interns treat the victims of a massive explosion at an apartment building, while Alex investigates the cause of the accident.

The new interns are dazzled by the skill level of fellow intern George, while Lexie helps keep his "repeater" status a secret; Meredith half-heartedly helps Lexie with her first emergency patient.

The hospital has a pipe break which causes a huge flood; Meredith quits therapy but Dr. Wyatt doesn't believe she is finished.

Major Owen Hunt returns to be the head of ER trauma; Meredith finds an old doll her mother gave her when she was 5.