Arlene Santana

Through Lexie, Meredith tries to get Derek interested in a patient's rare brain tumor; Callie ends up being annoyed when Mark and Arizona finally form a friendship; Teddy and Alex look into alternative surgeries for a superficial patient.

The hospital is hit with an unprecedented crisis; Meredith and Cristina's surgical skills are put to the test.

Issues surface when Derek's estranged sister, Amelia (Caterina Scorsone), visits unexpectedly; Meredith and Derek continue to try to ease Cristina back into surgery.

Amelia arrives at Seattle Grace to beg Derek to help with the gliosarcoma case; Cristina and Owen have heated arguments during marriage counseling; Alex realizes he needs to improve his people skills in order to be a good doctor.

Derek and April fight to find a solution for the hospital; Cristina works to respect the wishes of a dying boy's family; Arizona identifies with a teenager who is facing similar problems.

A gas tanker explodes on a highway, resulting in multiple injuries; Jo and Meredith try to help a frantic woman, whose child has a mysterious illness; Alex is forced to work with Jo's boyfriend.