Cristina discovers she is pregnant. George finds out the anesthesiologist has been drinking on the job, but when he tells Shepherd he is thrown out of surgery. George and Izzie catch Derek leaving the house in the morning after he sleeps with Meredith, and when asked who it was, Meredith says it's no one they know. Izzie and George think Meredith is trying to get Derek to favor her, and try to ice her out.

All of the interns are in awe when a woman comes in with a record breaking tumor, but it is so far advanced that the woman's prognosis is not good. Now that Bailey knows about Meredith and Derek's affair, their jobs are in jeopardy, and she strongly advises Meredith to end it. Meanwhile, Cristina and Burke's secret relationship gets more complicated, and when no one else can be reached, Izzie has to perform a major procedure on her own.

Meredith realizes she could be sued for making a mistake on a surgery. Her life gets more hectic hiding her mother's secret. George finds a towel in a patient, Izzie throws a party and Bailey catches Meredith having sex with Derek.

Cristina's encounter with Ellis Grey's former scrub nurse, who is now a patient at Seattle Grace, changes her forever. George becomes infuriated when he realizes that Izzie and Meredith treat him like their sister. An old part of Izzie's life will be revealed which makes her the subject of hospital gossip and Derek, Meredith, George and Alex have a patient with nails in his head. 

A bike race injures several people, one of whom is left brain dead. Cristina and Izzie want to use his organs for organ donation, but they find the organ harvesting process an emotional one. Meanwhile, George deals with an over-flirtatious patient, and Meredith has to deal with Izzie and George moving in, Alex showing off, and keeping Derek at arm's length.

In the pilot episode of Grey's Anatomy: Meredith Grey, Izzie Stevens, George O'Malley, Cristina Yang, and Alex Karev become interns at Seattle Grace Hospital. Meredith discovers that her one night stand was actually with one of her bosses and she and her new friends discover that being a surgeon isn't as easy or fun as they thought it would be.

TW: Rape George and Izzie move in with Meredith. Burke works harder to become the next Chief and takes Webber's advice to start going the extra mile for patients. Derek helps a rape victim while Meredith carries around the rapist's penis. Alex Karev becomes one of Bailey's interns and shadows Cristina for the day.