When a mission goes wrong, Sydney's is placed in danger and Marshall is the only one who can save her. Meanwhile, Dixon is exposed to a deadly pathogen released inside APO.

Sydney teams up with Renée - a fugitive on the CIA's most wanted list -- to track down the murderer of a close friend before the killer can strike again. Meanwhile, Jack enlists a reluctant new agent, Thomas Grace (Balthazar Getty), and Weiss struggles to decide whether or not to accept a promotion that would force him to leave his colleagues.

While Sloane awaits the outcome of his sentencing, Sydney's life is put in grave danger when Gordon Dean discovers that Rachel is still alive.

While the gang starts to learn more about the Prophet 5, Sloane is distressed to learn that Prophet Five's cure for Nadia is just as likely to kill her. Meanwhile, Devlin returns, the search for Anna Espinosa continues, Rambaldi's prophetic Page 47 resurfaces, and Sydney offers Renée a job at APO.

In the first part of [the] Alias two-hour finale event, 'Reprisal,' Sloane takes Marshall and Rachel hostage in order to discover a crucial clue to Rambaldi's ultimate endgame, as Sydney, Vaughn and APO race to stop him.