Season premiere

After learning that the man she has known as Michael Vaughn is under investigation and suspected of being a double agent, Sydney begins to question whether their business and personal relationship over the years had all been a lie. When she discovers that she's pregnant with Vaughn's baby, she becomes determined to uncover the truth about him. Meanwhile, because of Jack's past betrayal by Irina, he begins to worry that his daughter may suffer the same fate that he did.

Rating: 5.5/9

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.

Rating: 5.1/8

Sydney is forced to partner on a mission with new APO agent Thomas Grace. They discover that Rachel Gibson -- a spy suspected of being involved in activities against the U.S. -- has something shockingly in common with Sydney. Meanwhile, Dixon must accompany Sloane, who's given a 48-hour pass from prison to acquire a possible cure for his daughter.

Rating: 4.8/8

Sydney's life hangs in the balance when Gordon Dean discovers that Rachel -- aka Mockingbird -- is still alive. Meanwhile, Sloane awaits the outcome of his sentencing. Amy Acker (Angel) guest stars.

Rating: 4.7/8

Sydney and Tom discover that Reneé has stolen the cryogenic-type container, and they find themselves under siege by mercenaries who want the container's contents. Meanwhile, Sloane is forced to take matters into his own possibly devious hands to get himself reinstated into APO and to continue his quest to find a cure for daughter Nadia. Renee: Elodie Bouchez. Senator Lewis: Jennifer Hetrick. Luc: Patrick Bauchau. Dean: Tyrees Allen. Keach: Joel Bissonnette. Grace: Balthazar Getty.

Rating: 4.5/7

Sydney must guide a nervous and pensive Rachel on her first solo mission. Meanwhile, Sloane must decide whether or not to betray the trust he's recently earned with APO by honoring his agreement with Gordon Dean.

Rating: 4.3/7

Sydney and APO attempt to discover whom Gordon Dean is working for and what their end game is. Meanwhile, when the group claiming to have a cure for daughter Nadia continues to play mind games with him, Sloane struggles for control. Mia Maestro and Amy Acker guest star.

Rating: 4.4/7

After Rachel has a fling that inadvertently compromises a mission, she and Sydney are forced to team with Julian Sark (David Anders) to prevent a deadly micropulse bomb from getting into the hands of a dangerous mercenary. Meanwhile, Jack and a former lover -- an MI-6 agent -- fight for their lives after being captured.

Rating: 4.3/7

Sydney is reunited with Vaughn after being kidnapped and put in a hypnotic state in order to retrieve information from the depths of her mind. But unbeknownst to Sydney, her captor is a familiar face with a vested interest in Sydney's future and the future of her unborn child.

Rating: 3.8/6

In the two-hour return event, featuring the episodes "S.O.S." and "Maternal Instinct," Jack calls on former Agent Weiss and the APO team to search for Sydney after receiving a distress call from her. But Jack believes that a larger conspiracy may be in play, thwarting their attempts to rescue her. Meanwhile, Tom's suspicious actions may suggest he has a hidden agenda, Irina Derevko is a surprise partner to Jack and a very pregnant Sydney on a mission to retrieve "The Horizon" - but her allegiances still remain in question -- and Sloane is forced to scramble when Devlin suspects a mole is working inside APO.

In the two-hour return event, featuring the episodes "S.O.S." and "Maternal Instinct," Jack calls on former Agent Weiss and the APO team to search for Sydney after receiving a distress call from her. But Jack believes that a larger conspiracy may be in play, thwarting their attempts to rescue her. Meanwhile, Tom's suspicious actions may suggest he has a hidden agenda, Irina Derevko is a surprise partner to Jack and a very pregnant Sydney on a mission to retrieve "The Horizon" - but her allegiances still remain in question -- and Sloane is forced to scramble when Devlin suspects a mole is working inside APO.

New mother Sydney is back on the job ahead of schedule when Will (Bradley Cooper) is kidnapped by Anna (Gina Torres); Sloane's odds of finding a cure for Nadia improve.

Rating: 4.4/7

This episode was nominated for an Emmy award for Outstanding Hairstyling for a Series (Michael Reitz, Head Hairstylist, Katherine Rees, Key Hairstylist, Shimmy Osman, Key Hairstylist).

Sloane is distressed to learn that Prophet Five's cure for Nadia is just as likely to kill her. Meanwhile, the search for Anna Espinosa continues, Rambaldi's prophetic Page 47 resurfaces, and Sydney offers Ren&eactue;e a job at APO.

Rating: 3.8/6

Sydney must beat arch-nemesis Anna Espinosa to the punch when a mysterious chip found implanted in Renée is tied to Vaughn. Meanwhile, Sloane struggles with ghostly visions while working for Prophet Five.

Rating: 4.2/7

Sydney must stay undercover and partner with Sark to track down Rambaldi's final clue before Prophet Five finds it. Meanwhile, Vaughn sees daughter Isabelle for the first time, and Rachel discovers Tom's secret.

Rating: 3.9/6

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.

Rating: 4.5/7

Sydney and Jack must find a way to keep Sloane and Irina from putting their deadly plan into action.

Rating: 4.5/7

The two-part finale was nominated for an Emmy award for Outstanding Stunt Coordination (Shauna Duggins, Stunt Coordinator).