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.