S4, E10: Dixon enlists Sydney to help him prove that Sloane is double-crossing the CIA and using APO to steel the Blackwell Index, a master blackmail list, and to reconstruct the Alliance. Sydney makes her way into Sloane's house so as to copy the encryption key from his secure phone and crack his calls. When Nadia finds her, she becomes disappointed in her sister. Meanwhile, Vaughn discovers something disturbing about his father when he visits his comatose uncle.