Grey's Anatomy: Season 3, Episode 20

3 - 20: Time After Time

When Izzie's daughter is brought to the hospital for leukemia treatment, Izzie is asked to donate her bone marrow in support. Derek finds that Meredith stands in his way of becoming chief. Marlowe continues to intrude on Burke and Cristina's lives with an impending surgery Burke will perform. Meredith becomes closer to her stepmother (Mare Winningham). Parents claiming to be Ava's come in to identify her but learn she is not theirs.