Arlene Santana

When a burn victim unexpectedly dies in the ER, all the Mercy West and Seattle Grace residents must defend their actions in hope of saving their jobs.

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

Owen puts the residents through a rigorous trauma certification drill; Cristina is left alone to monitor an ill lung transplant patient.

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.