Alias season 4 episode 17
A Clean Conscience
Nadia's former caretaker, Sophia, has been severely beaten. She contacts Nadia and asks to meet her. Sloane is told by Sophia that she was beaten up, because someone is trying to track Nadia down, so he and Jack decide to tell their daughters the truth – Elena Derevko, the third and the most cruelest of the Derevko sisters, has been surveilling both Sydney and Nadia for a decade. Meanwhile, Jack's doctor advises him to tell Sydney about his illness.
