Sydney's secret double agent status is jeopardized after she smuggling a biotech engineer into SD-6 from her mission in Berlin. Will meets a woman who confesses that she was having an affair with Danny shortly before his death. Vaughn informs Sydney that her father may be working for a third secret operative agency.

After making a shocking discovery in the desert, Sydney agrees to submit to an experimental procedure conducted by an eccentric doctor, designed to retrieve her lost memories. But while Jack and Vaughn look on, Sydney's mind proves surprisingly resistant to letting her remember her missing time -- and the process of recovering it could end up killing her. Meanwhile, Lauren makes a great sacrifice in order to make her alibi believable to Lindsey after breaking Sydney out of NSC custody, and Sloane finds himself boxed in by an unlikely enemy -- one who wants to see Sydney Bristow eliminated permanently

Sydney attempts to rescue Dixon's kids after they are kidnapped by Sark, Lauren's status as a double agent is put to the test when she learns that she has to work with her father, and Sloane is framed as a CIA mole.