Molly Kidder

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.

Meredith and Derek rediscover the morning-after side of their relationship; the chief learns the hospital has slipped in the national rankings.

The surgeons work as a team to free a boy from a hardening block of cement; Izzie helps Alex care for an ailing Rebecca; Meredith and Derek have one last chance at a positive result in their clinical trial.

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.

Addison (Kate Walsh) returns to Seattle Grace to perform a surgery and is surprised to learn about the changes in her former coworkers' lives.

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