Sheldon fears the worst when a little girl goes missing from the ER; Addison and Jake have a disagreement about one of his patients; and a new doctor joins the team at Saint Ambrose. Meanwhile, Stephanie questions Sam about his past with Addison.

In this Addison-centric episode, her role as a parent is challenged when Henry's biological mother reappears and asks to be more involved in her young son's life. Meanwhile Addison reconnects with her mentor, who shares a very painful secret.