Derek asks Addison to work with his pregnant patient while Archer recuperates from surgery; Bailey and Naomi work together to find the cause of Sam's sudden asthma attack; Cooper, Violet and Pete treat a woman with postpartum depression.

Cooper and Charlotte take Erica to Seattle Grace to meet with Derek, Lexie and Amelia regarding a very risky surgery; Scott tells Violet that he would like to take their relationship to the next level; and Addison finds herself caught in the middle of Sam and Jake's fight about a patient. Meanwhile, Sheldon warns Sam to be cautious as he deals with the return of his sister, Corinne.