Sydney, Vaughn, Jack and Dixon get a new boss, Sydney and Vaughn question whether they’ll ever be able to reconcile their relationship, Sydney learns a terrible secret about her father, and Nadia is reluctant to return to the spy world since learning the truth about her father – Sloane. Angela Bassett (“How Stella Got Her Groove Back,” “Waiting to Exhale,” “What’s Love Got to Do with It”) guest stars as CIA Director Hayden Chase. Mia Maestro joins the cast as Sydney’s half-sister, Nadia Santos.

Sydney, Vaughn, Jack and Dixon get a new boss, Sydney and Vaughn question whether they’ll ever be able to reconcile their relationship, Sydney learns a terrible secret about her father, and Nadia is reluctant to return to the spy world since learning the truth about her father – Sloane. Angela Bassett (“How Stella Got Her Groove Back,” “Waiting to Exhale,” “What’s Love Got to Do with It”) guest stars as CIA Director Hayden Chase. Mia Maestro joins the cast as Sydney’s half-sister, Nadia Santos.

Sydney must convince a murderer to fall in love with her in order to locate a stolen code-breaker, Vaughn fears Weiss may have been killed, and Sydney and Jack argue over telling Nadia the truth about Irina.

Sydney is suspicious over Sloane’s fatherly concerns for Nadia, and Sydney and Nadia go undercover as wealthy heiresses to find the location of a deadly chemical.

Sydney and Vaughn go undercover to track down a deadly bio-weapon, Vaughn’s inner-demons over deceased wife Lauren begin to surface, and Nadia asks Jack about her mother, Irina.

When Sydney is infected with a deadly hallucinogen, it’s up to Vaughn and Jack to find the antidote before her resultant violent behavior consumes her.

In order to save Nadia, Sydney must bring down former nemesis Anna Espinosa, while Vaughn confronts Mr. Sark. Gina Torres (“24”) returns in the role of Anna Espinosa and David Anders makes a guest appearance as Julian Sark.

Sark asks Vaughn to grant a very disagreeable request before helping him and Sydney track down Anna Espinosa, and Jack ponders risking Nadia’s life in order to extract information about Anna’s whereabouts. Gina Torres (“24”) guest stars as Anna Espinosa and David Anders appears as Julian Sark.

Sydney and Vaughn go undercover as a married couple in "suburbia" in order to confiscate a deadly weapon that could set society back to the dark ages.

Sydney’s relationship with Nadia is threatened when she believes that Sloane is trying to rebuild the Alliance, and Vaughn learns a startling secret about his father. Angela Bassett (“How Stella Got Her Groove Back,” “Waiting to Exhale,” “What’s Love Got to Do with It”) guest stars as CIA Director Hayden Chase.

Sydney places the life of an American civilian in peril, Jack plans a deadly visit with an old friend, and Vaughn uncovers more disturbing secrets about his father.

Nadia’s past with a man who is the target of an investigation places her life and the lives of her team in danger, and Vaughn discovers someone with ties to both his father and Nadia. Sonia Braga (“American Family,” “Kiss of the Spider Woman”) guest stars.

Sydney and Vaughn risk losing everything as they continue their search for the truth about Vaughn's father, Jack and Sloane mysteriously conspire with each other - and against Sydney and Vaughn - and Jack faces a potentially deadly choice that will forever change his life and Sydney's.

Sydney learns shocking news about her mother’s death from Katya Derevko, Vaughn becomes a rogue agent and steals a device in order to learn the truth about his father, and Marshall questions Jack’s health. Isabella Rossellini guest stars as Katya Derevko. Joel Grey (Broadway’s “Wicked,” “Cabaret”) makes a guest appearance.

Sydney is forced to side with Sloane in order to catch the man who has been impersonating him and Nadia worries that her father may rediscover a past obsession.

After a mission goes south on Sydney, Marshall may be the only person who can save her, and Dixon is exposed to a deadly pathogen. Sydney’s life hangs in the balance when a mission goes awry -- and Marshall, surprisingly, is the only one who might be able to save her. Meanwhile, Dixon is exposed when a deadly pathogen is released inside APO.

Sydney and Nadia discover that Sophia has been severely beaten. Sloane fears for Nadia's life when he learns the reason for the beating.

Sydney is shocked when she learns that Jack chose not to tell her that he’s terminally ill, and Nadia’s orphanage caregiver continues her convalescence at Sydney’s apartment.

Sloane’s impersonator resurfaces and sets his sights on Rambaldi and shocking revelations are brought to light about the real Sloane.

APO learns the awful truth about Sophia, an agent’s life hangs in the balance, Sydney and Nadia become concerned that Sloane’s obsession with Rambaldi may have been renewed, and Jack has an unsettling meeting with Katya Derevko.

After learning that Irina Derevko is alive, Sydney, Jack, and Nadia must find her in order to thwart Elena Derevko’s deadly Rambaldi endgame. Meanwhile, Dixon’s condition worsens.

The Rambaldi end game is put into motion by Elena Derevko and it’s up to Sydney, Jack, Irina, Vaughn, and Nadia to save the world from its catastrophic effects on the season finale.