Amrapali Ambegaokar

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.

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

Derek prepares to perform his first surgery since his breakdown; Owen has a PTSD episode which injures Cristina and puts their relationship in jeopardy.

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.

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

Cristina and Meredith try to put their differences aside to treat a prisoner on death row with a serious brain injury; Bailey is put on her heels by a new pediatric surgeon.