Sydney Bristow discovers that her job as an agent for SD-6, a top-secret division of the CIA, is not what she thought it was. Sydney's father, Jack, also tells her the truth about his work and she, enraged, seeks help from real CIA and is hired as their double agent under the command of Agent Vaughn. From now on, her job is really simple: she needs to complete her cases at SD-6 while reporting her findings back to the CIA.

On her first mission as a double agent, Sydney is sent to Moscow to retrieve some stolen files about nuclear bomb. Meanwhile, Will continues to grow obsessed with Danny's death and starts his own investigation even though Sydney asked him not to.

Sydney is sent to Madrid to retrieve a 500-year-old sketch that contains a set of numbers and meets up with her deadly nemesis, K-Directorate agent, Anna Espinosa. Meanwhile, Will digs deeper into the cause of Danny's death and finds some odd information.

Sydney and Dixon are sent on a dangerous case involving the safety of the United Commerce Organization. Francie gets suspicious about Charlie and spies on him. Meanwhile, Will continues to investigate the truth about Danny's murder.

Sydney's cover in SD-6 is put in danger after smuggling a wrong biotech engineer into SD-6 from her mission in Berlin. Meanwhile, Will's investigation into Danny's murder leads him to a woman named Kate Jones, who may have information about the killing. Sydney's starts to doubt where her father's true allegiances lie.

Sydney goes undercover in a mental institution to meet a man programmed to be an assassin. Meanwhile, back home in LA, Will discovers the true identity of "Kate Jones" and Francie learns the truth about Charlie.

Trapped in the Romanian asylum run by the Russian spy group, K-Directorate, Sydney befriends amnesiac agent Mark Shephard. Sloane and Alliance representative Alain Christophe come to conclusion that SD-6 has mole(s) and plan a trap.

Sydney must undergo an extensive lie detector test to prove her loyalty to SD-6 while at the same time she is trying to find connection between a 500 year old Rambaldi sketch and a machine. In the meantime, Will gets deeper into the secrets while investigating Danny's death.

Sydney's life and cover as a double agent is placed in mortal danger when Sloane starts assuming that she is the mole. Dixon's life is at stake after the mission that went wrong. Meanwhile, Will realizes that his investigation of Kate Jones may be more dangerous than he thinks after he gets a call from the person "on the other side" of her pin.

After she manages to escape a certain death at SD-6 and still manages to maintain her cover as double agent, Sydney is sent on a private island to find new identity of Ineni Hassan, an ex weapon smuggler and previous head of weapons resources of SD-6. Things go south for Sydney after she discovers that Jack got into trouble on a mission in Cuba, and in the meantime, Will Tippin focuses his investigation on SD-6, whose name he heard for the first time thanks to the bug from Eloise Kurtz.

Sydney is sent to Greece to retrieve information about new weapons that are being produced by a young tycoon. Meanwhile, Vaughn plans to report Jack for his apparent involvement in murders of many CIA agents and by doing so, he crushes Sydney's newly found admiration for her father.

When former SD-6 agent McKenas Cole with his crew of bandits take over SD-6, Sydney has to forget her previous plan about quitting the agency and has to focus on her mission with Jack to save their colleagues. In the meantime, as he was about to quit his work on a story, Will Tippin gets an unexpected push to continue from the third party.

Vaughn disobeys the CIA in order to infiltrate SD-6 when he receives a desperate plea for help from Dixon. At SD-6, Cole continues his vendetta against Sloane and his search for device in possession of SD-6. Elsewhere, Will continues his work on story.

After the SD-6 finds out that another terrorist organisation was attacked at the same time as them, Sydney and Dixon are sent to Las Vegas, and later Moscow, to try to find something that will bring SD-6 closer to identity of The Man. All in the same time, Sydney learns some shocking news about Francie's fiancé, Jack tries to be a better father to Sydney and Will begins his journey in discovering SD-6.

Vaughn presents Sydney with a moral dilemma that includes Sloane's ill wife, Emily, in order to fulfill the mission whose outcome is an unpleasant surprise to everyone. SD-6 goes after Will when he comes too close. Meanwhile, Francie is dealing with her broken heart.

Department of Special Research gained interest in Sydney's role involving the page 47 and they began their own investigation regarding it. To save herself, Sydney needs to steal 500 year old Rambaldi codes from Vatican to decipher Rambaldi's prophecy. Meanwhile. Sloane gets suspicious that one of the Alliance's members switched sides and is now working with The Man.

Sydney is heavily questioned by the FBI concerning her past and her current activities at SD-6. Fearing that the FBI might detain her longer, Jack and Vaughn must find a way to make her escape before she blows her cover with SD-6...

After she managed to prove her innocence to FBI, Sydney is sent to Vienna to retrieve data from SD-6 spy in Russian Embassy. There she runs into Noah Hicks, her ex who broke her heart and left her without a word few years earlier. Meanwhile, Sloane promises Sydney to help her find her mother and Jack is losing his mind because of it.

As Sydney and Noah go to Cape Town to get some data on "The Man" , Sloane begins to question where Noah's true allegiances lie when his team finds some suspicious bank activities of his. Vaughn goes to Colombia to get information about Russian assassin known under the codename "Snowman" whose recent mission was to kill Kjasinau, a.k.a. "The Man". While Sydney is getting closer to the truth about her mother, Will and Francie confront her about the airline ticket they found in her coat.

Francie is having a rat problem in her house and gives an inspiring speech about catching them which gives Sydney idea how to catch Khasinau. She and Vaughn set up fake transaction for a Rambaldi artifact with Sark, but their job is compromised when Sloane sends SD-6 agents to steal the presumed second vial. Meanwhile, Will learns the truth about his kidnapping and Jack Bristow has no option but to help him.

While Sloane is desperate to buy few more days for his wife, Will, with a help of Jack, sets up a meeting with his contact "Deepthroat" in Paris. As the luck would have it, Sydney and Dixon will be there at the same time trying to steal a very important document from Khasinau aka "The Man" and his right hand, Mr. Sark, who was just recently in the custody of the SD-6.

Sloane must take a difficult decision in order to get to the Alliance's council. After being captured by Sark, Tippin is tortured by a Taiwanese would-be dentist to extract secrets. Sydney, who has to beware her colleague Dixon, assist her father trying to save Tippin. However, after losing Vaughn when the lab exploded, she is in for a surprise...

Sydney finds herself face-to-face with her long-lost mother, Irina Derevko, whose intentions for her daughter are made chillingly clear. However, Sydney manages to escape and rejoin Jack and Will in their escape from Taiwan. After arriving back in Los Angeles, Sydney continues her search for Vaughn, not knowing if he is dead or alive after being swept away by a wall of water in Taipei. Will's life is forever changed when he learns the truth about SD-6 and Sydney's life as a double agent. Also, Dixon must decide whether or not to inform Sloane of Sydney's suspicious activities. But Jack intervenes and covers for Sydney who later finds Vaughn who helps her try to track down her mother Irina who's searching for a Rimbaldi artifact called 'the Bible.'

After turning herself in to the CIA, Irina won't communicate with anyone - except her daughter. Sydney refuses to cooperate, until a mission goes awry and crucial information falls into the wrong hands. Now, against Jack's wishes, Sydney must face Irina and find out what She knows.

Sydney must travel to Sri Lanka to outwit Sark in order to find a crucial piece of Intel from a computer disk that she recovers from Rabal. Meanwhile, Jack faces Sydney's mother for the first time in almost 20 years in her prison cell to discuss Sydney's well being. Also, Will finally meets Vaughn, and Sloane is haunted by his wife's death when someone begins sending him anonymous letters which have Emily's handwriting on them.

Past demons revisit all the characters as Sloane becomes confused and desperate over clues that his wife may not be dead. At the same time, Will meets a woman who claims to know the truth about SD-6. And Jack tries to convince Sydney that Irina is setting the stage to betray them and will go to any lengths to prove it.

Jack's decision to sabotage Sydney's last mission while pinning it on Irina not only brings him closer to his daughter - it sends his ex-wife to death row. But his foolproof plan begins to unravel when Vaughn begins to put the pieces together - and Sydney makes a startling discovery about her childhood.

Sydney's fury at Jack's present betrayal and past sins leads her father to a desperate act to prove his love for her. Meanwhile, Vaughn - after enlisting Will in a seemingly benign CIA request - learns that a mission He and Sydney engaged in could have disastrous consequences for their health.

As Vaughn's life hangs in the balance, Sydney has no choice but to turn to Sark for help in securing an antidote for the virus. But when Sark demands She help him to kill Arvin Sloane in exchange for his assistance, Sydney faces a decision that could expose her as a double agent.

Sark's alliance with SD-6 suddenly puts Sydney at risk of being exposed as a double agent. She has no choice but to cooperate with his plan, until his alliance with Sloane sends several nuclear weapons into the wrong hands. Now, only Irina holds the key to unraveling Sark's agenda - and She refuses to cooperate.

Still trapped in hostile territory in Pakistan, Sydney, Jack, and Irina continue their search for the missing nuclear warheads held by PRF's leader Gerard Cuvee. After several misadventures, they arrive at Cuvee's stronghold, only to be betrayed by Irina. Back in the USA, Vaughn wants to mount a secret rescue mission to Pakistan before Kendell authorized the Indian army to launch an air strike on the facility with Jack and Sydney held captive inside. Meanwhile, Sloan decides to pay off his unknown blackmailer.

Backed into a corner, Sark cuts a desperate deal Sloane using Sydney to recover a state-of-the-art surveillance system. But when the plan goes awry, SD-6 sends Marshall with Sydney on her next mission... giving the CIA no choice but to extract the op-tech specialist. Now Sydney faces the consequences of "waking up" Marshall - and possibly destroying his life in the process.

When Sydney learns that Marshall has been kidnapped, she struggles against a heartless Sloane to bring Marshall back whom is being tortured by the same Taiwanese torturer Dr. Lee "Suit and Glasses" to uncover the code for the top secret ECHELON security system whom tries to stall for time. Sydney and Dixon are instead sent to Ho Chi Minh City, Vietnam to recover the hard drive for ECHELON. Meanwhile, Kendall and the rest of the CIA frantically tries to prevent SD-6 from gaining access to ECHELON... and Jack realizes that the only one who can help them is Irina.

Sydney and Vaughn reach a crossroads as they try to turn a professional relationship into a personal one during a mission to recover an experimental gyroscope. Meanwhile, Jack struggles to outwit the persistent SD-6 security expert, Ariana Kane, as she tightens the noose of suspicion around him of being Sloan's blackmailer.

The entire world of 'ALIAS' is turned upside down. Sloane disappears mysteriously and Anthony Geiger becomes the new head of SD-6. As the Bristows struggle to keep their secrets safe and stay one step ahead of Geiger, Will and Francie make a startling discovery of their own while Francie prepares to open her new restaurant. After an airborne mission, Sydney uncovers crucial information that could shut down SD-6 and bring down the entire Alliance.

When a young CIA agent dies, suspicion immediately falls on her parter and lover, agent Jim Lennox. But after Sydney rescues Lennox from captivity, She trikes up an instant connection as they discover shared wounds - realizing They've both lost someone they love to the job. Yet even her judgment is thrown when Vaughn and Jack discover that Lennox was pursing a technology that allows people to change their appearance. Now Sydney must ask herself: is this the real Jim Lennox - or is his double?

Sydney finally has the opportunity to leave the CIA for good, but a startling phone call from Sloane, combined with the kidnapping of a brilliant mathematician, brings her back into the fray.

When Sloane gets his hands on a terrifying Rimbaldi weapon that causes internal spontaneous combustion, Sydney must turn to a betrayed and hurt Dixon for help. But when her ex-partner refuses any assistance, She has no choice but to carry out the mission herself. When Sydney is captured, Vaughn must persuade Dixon to help the CIA rescue Sydney from an Afghan warlord's camp.

When Sydney learns that Vaughn is under investigation for being a double agent, Jack and Irina forge an unlikely partnership in their attempt to get their daughter out of the CIA for good. Kendall learns that Sark and Sloane are attempting to get their hands on a Rambaldi manuscript detailing the works of the human heart, so he sends Jack and Irina to Bangkok to learn more, and then to Panama to capture Sloane. But Irina betrays Jack and escapes from custody... this time for real.

Following her betrayal, the CIA try desperately to track down Irina Derevko. Their trail on Derevko leads them to Stuttgart and closer to Sark and Sloane, even as Sloane contemplates giving up his quest to complete Rambaldi's work in order to stay with his wife, Emily.

When the CIA intercepts a secret message, Sydney discovers that the life of Neil Caplan, the mathematician still held captive by Sloane and Irina, may be in danger from the most unlikely source: his wife Elsa whom Jack has arrested, forcing Sydney to try to clear Elsa's name by going on her own mission to Moscow and Spain to try to rescue Neil Caplan. Meanwhile, Sloane becomes obsessed with finding out who accidentally killed Emily, and Sark makes contact with the Francie impostor to locate the person responsible... by using Will to infiltrate the CIA satellite surveillance systems.

As Dixon struggles with the death of his wife, He refuses to take time off from work until Sloane is brought to justice. But Sydney worries that Dixon's repressed rage could cause more harm that anything Sloane could do.

Sydney finds herself racing to clear Will's name when the Francie impostor frames him for the CIA intelligent leak by making him appear to be the other double of the Helix project. But Sark makes matters worse when he sends a team to extract Will, to make it look that he's guilty. Meanwhile across the globe, Irina and Sark discover a stumbling block could turn into an opportunity... with Sydney's cooperation.

Sydney must confront her mother, who tells a clue about "some Rambaldi artifacts" in Zurich, but it was a trap to capture Jack. As Sloane keeps Jack hostage, Vaughn and Sydney go to Stockholm to capture Sark, who reveals the hideout in Mexico City. Meanwhile, Tippin discovers that Francie is in fact a "double" and is the one who framed him...

Sydney's emotions are turned inside-out when she once again comes face-to-face with Allison Doren, the murdered Francie's doppelgänger, who was presumed dead but is now a key assassin working for the Covenant. Meanwhile Lauren's search for Lazarey's murderer leads her closer to discovering the connection to Sydney, and Sydney begrudgingly is assigned as Sloane's CIA handler.

The identity of the mysterious "St. Aidan" forces Sydney to pull a stunned Will Tippin out of witness protection for help in finding Lazarey to clear her name. But the pursuit sends the two old friends on a collision course with Allison, the Francie impostor who ruined both their lives. Meanwhile, a jealous Lindsey arrests Jack and Vaughn as conspirators in Sydney's escape from NSC custody. Sloane, still under pressure from Lindsey, puts a plan in motion to eliminate Sydney, and Dr. Brezzel has an unpleasant run-in with Sark whom is also looking for Sydney.

One month later, with Sydney on maternity leave, she gets forced back into the field when her old enemy, Anna Espinosa, returns after she's secretly sprung from prison by Peyton who gives her a job offer to work for Prophet Five whose leaders have secretly contact with Sloan to get him to set up Sydney in exchange for getting the cure for Nadia. Anna decides that to get at Sydney is that she needs to go through her friends, leading to Anna to abduct Will Tippen. Sydney, along with APO, is forced to try to find Anna and save Will before he's killed unaware that Prophet Five has bigger plans for Syd, to take a sample of her DNA.

One month later, with Sydney on maternity leave, she gets forced back into the field when her old enemy, Anna Espinosa, returns after she's secretly sprung from prison by Peyton who gives her a job offer to work for Prophet Five whose leaders have secretly contact with Sloan to get him to set up Sydney in exchange for getting the cure for Nadia. Anna decides that to get at Sydney is that she needs to go through her friends, leading to Anna to abduct Will Tippen. Sydney, along with APO, is forced to try to find Anna and save Will before he's killed unaware that Prophet Five has bigger plans for Syd, to take a sample of her DNA.

The identity of the mysterious "St. Aidan" forces Sydney to pull a stunned Will Tippin out of witness protection for help in finding Lazarey to clear her name. But the pursuit sends the two old friends on a collision course with Allison, the Francie impostor who ruined both their lives. Meanwhile, a jealous Lindsey arrests Jack and Vaughn as conspirators in Sydney's escape from NSC custody. Sloane, still under pressure from Lindsey, puts a plan in motion to eliminate Sydney, and Dr. Brezzel has an unpleasant run-in with Sark whom is also looking for Sydney.

Sydney finds herself racing to clear Will's name when the Francie impostor frames him for the CIA intelligent leak by making him appear to be the other double of the Helix project. But Sark makes matters worse when he sends a team to extract Will, to make it look that he's guilty. Meanwhile across the globe, Irina and Sark discover a stumbling block could turn into an opportunity... with Sydney's cooperation.

Past demons revisit all the characters as Sloane becomes confused and desperate over clues that his wife may not be dead. At the same time, Will meets a woman who claims to know the truth about SD-6. And Jack tries to convince Sydney that Irina is setting the stage to betray them and will go to any lengths to prove it.

While Sloane is desperate to buy few more days for his wife, Will, with a help of Jack, sets up a meeting with his contact "Deepthroat" in Paris. As the luck would have it, Sydney and Dixon will be there at the same time trying to steal a very important document from Khasinau aka "The Man" and his right hand, Mr. Sark, who was just recently in the custody of the SD-6.

Vaughn presents Sydney with a moral dilemma that includes Sloane's ill wife, Emily, in order to fulfill the mission whose outcome is an unpleasant surprise to everyone. SD-6 goes after Will when he comes too close. Meanwhile, Francie is dealing with her broken heart.

Sydney is sent to Madrid to retrieve a 500-year-old sketch that contains a set of numbers and meets up with her deadly nemesis, K-Directorate agent, Anna Espinosa. Meanwhile, Will digs deeper into the cause of Danny's death and finds some odd information.

Sydney must confront her mother, who tells a clue about "some Rambaldi artifacts" in Zurich, but it was a trap to capture Jack. As Sloane keeps Jack hostage, Vaughn and Sydney go to Stockholm to capture Sark, who reveals the hideout in Mexico City. Meanwhile, Tippin discovers that Francie is in fact a "double" and is the one who framed him...

Sydney's cover in SD-6 is put in danger after smuggling a wrong biotech engineer into SD-6 from her mission in Berlin. Meanwhile, Will's investigation into Danny's murder leads him to a woman named Kate Jones, who may have information about the killing. Sydney's starts to doubt where her father's true allegiances lie.

Sloane must take a difficult decision in order to get to the Alliance's council. After being captured by Sark, Tippin is tortured by a Taiwanese would-be dentist to extract secrets. Sydney, who has to beware her colleague Dixon, assist her father trying to save Tippin. However, after losing Vaughn when the lab exploded, she is in for a surprise...