#404 - Ice
Sydney goes undercover as an earthy social worker and Vaughn as a semi-tipsy priest to track down a deadly new bio-weapon. Meanwhile, Syd is frightened when Vaughn's inner-demons regarding Lauren come to the surface, and Nadia turns to a reluctant Jack to learn truths about her mother.
Original US Airdate: January 19th, 2005

#405 - Welcome To Liberty Village
In order to gain intel on a secret training camp for spies wishing to infiltrate the states, Sydney and Vaughn pose as a married couple in a 10 mile fortified city. Meanwhile, Jack and Marshall try to uncover why one of Irina's old KGB contacts wants the books which contained her missions when she was still an operative.
Original US Airdate: January 26th, 2005

#406 - Nocturne
Sydney becomes infected with a mind-altering and potentially deadly hallucinogen, causing her to slowly lose touch with reality. Vaughn and Jack must scramble to find an antidote before Sydney's hallucinations, paranoia and resultant violent behavior threaten her life and the lives of those around her.
Original US Airdate: February 9th, 2005

#407 - Detente (Featuring music by Michael Lord)
Sydney and Nadia go undercover to trace the sales of a deadly weapon known only as 'Black Thorine', which has the power to amplify the explosive potential of virtually all explosive devices. Meanwhile, Sloane is forced to consider the consequences of his past, and evaluate his place at the APO division.
Original US Airdate: February 16th, 2005

#408 - Echoes (Guest starring Gina Torres and David Anders)
When Nadia is kidnapped by a mysterious rogue agent, Sydney is forced to go head-to-head with her former K-Directorate nemesis Anna Espinosa who also happens to be an avid believer in the works of Milo Rambaldi. Meanwhile, Vaughn confronts his own inner demons when he is forced to deal with the insidious Mr. Sark who is still in CIA custody.
Original US Airdate: February 23rd, 2005

#409 - A Man Of His Word (Guest starring Gina Torres and David Anders)
With Nadia in a coma, its up to Sydney to try and track down Anna Espinosa to find a cure. However, in doing so she must impersonate the deceased Lauren Reed and deal with her Covenant handler. Meanwhile, Arvin Sloane comes face-to-face with Sark for the first time since taking over APO.
Original US Airdate: March 2nd, 2005

#410 - The Index (Guest starring Angela Bassett)
While trying to keep tabs on Sloane's activities within APO, Sydney comes to the conclusion that he is actually in contact with some of his old SD-6 associates and is actively trying to rebuild the Alliance. But to get concrete evidence, she must raid Sloane's home...without Nadia finding out.
Original US Airdate: March 9th, 2005

#411 - The Road Home
During a mission to Germany, Sydney inadvertently places the life of an American civilian in jeopardy and must do all she can to get him out of harm's way. Meanwhile, Jack plans a deadly visit with an old friend and Vaughn uncovers some unsettling secrets about his father.
Original US Airdate: March 16th, 2005

#412 - The Orphan (Guest starring Sonia Braga)
When APO is tasked with hunting down one of her former associates, Nadia's loyalties are divided. Does she help her friend, or do her duty and stop him from selling on a deadly new technology. At the same time, Vaughn continues to investigate his fathers death at the hands of Irina Derevko.
Original US Airdate: March 23rd, 2005

#413 - Tuesday
After an operation in Havana goes south, Sydney is buried alive and Dixon is left unconcious after a deadly pathogen is released inside APO...cutting Sydney off from all help. Her only hope is for Marshall to head into the field by taking on an alias: he's to become Jack Bristow.
Original US Airdate: March 23rd, 2005

#414 - NightIngale
When they learn of Michael Vaughn's rogue quest to learn the truth about his father, Jack and Sloane realise they can secretly use him for their own schemes. But when a mission goes wrong, it is Sydney's life that hangs in the balance.
Original US Airdate: April 6th, 2005

#415 - Pandora (Guest starring Isabella Rossellini)
Sydney begins working with her aunt, Katya Derevko, in order to uncover the truth about why Jack had Irina killed. During their investigation, the duo discover that it is possible Irina was set-up...by Sloane! Meanwhile, Vaughn's status within the CIA is officially classed as rogue.
Original US Airdate: April 13th, 2005

#416 - Another Mister Sloane (Guest starring Joel Grey)
Pleading guilty to the claim that he is responsible for Irina's death, Arvin Sloane heads into the field in order to clear his name and to discover who has been impersonating him. However, when Nadia realises Sloane's passion for Rambaldi might have resurfaced, even she doubts his intentions.
Original US Airdate: April 20th, 2005

#417 - A Clean Conscience (Guest starring Sonia Braga)
Sofia Vargas, the woman who cared for Nadia as a child, arrives in L.A and is beaten to within inches of her life. Naturally, Nadia wants to investigate but Sloane fears for her safety when he discovers the reason for the attack. Elsewhere, Jack seeks medical help for his radiation sickness.
Original US Airdate: April 27th, 2005

#418 - Mirage (Guest starring Sonia Braga)
Sydney uncovers the truth behind Jack's mysterious illness and in order to help him she is forced to take on an alias: Irina Derevko, her mother. Meanwhile, when it becomes clear that APO has been compromised, Nadia and Weiss head into the field to plug the leak...but it might be closer to home than they realise.
Original US Airdate: May 4th, 2005

#419 - In Dreams (Guest starring Joel Grey)
In her directorial debut, Jennifer Garner leads this pivotal episode to a climax as the Sloane double (nicknamed the Sloane-Clone) continues his quest for Rambaldi. During the race to track him down, the team discovers an atrocity commited by the real Sloane when he was supposedly 're-formed'.
Original US Airdate: May 11th, 2005

#420 - The Descent (Guest starring Sonia Braga and Isabella Rossellini)
When APO discovers that Sofia Vargas is actually Elena Derevko, the call goes out to track her down before her deadly agenda can be carried out. Meanwhile, Jack meets with Katya Derevko and Nadia fears that her father has re-discovered the wonders of the prophet Rambaldi.
Original US Airdate: May 18th, 2005

#421 - Search and Rescue (Guest starring Angela Bassett and Lena Olin)
With Sloane now a renegade, Dixon informs Syd and Nadia that he saw Irina in a former Covenant jail-cell and that she is being kept alive by her sister Elena. Jack then leads a tactical mission to free her mother and to stop Sloane from carrying out the Rambaldi apocalypse.
Original US Airdate: May 18th, 2005

#422 - Before The Flood (Guest starring Sonia Braga and Lena Olin)
The Rambaldi Muller device has been activated, the Russian city of Savogda is in chaos and Elena is one step closer to her endgame. Syd, Nadia, Vaughn and Jack head into the city to disarm the device. Meanwhile, despite Irina's warnings, Vaughn finally pops the question.
Original US Airdate: May 25th, 2005