Episode list

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.

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...

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...

When a mission to Cuba goes wrong, Sydney is attacked and placed in serious danger of being buried alive in a sealed coffin. Back in Los Angeles, Dixon is exposed to a deadly pathogen released inside APO which is currently in lock down due to the toxin and Marshal (not being in the building at the time due to his home life problems), is the only one who can get to Sydney and save her. Only with com link help from Jack, Vaughn and the others at APO, the socially awkward and field inexperienced Marshal has to finish a very important mission on his own before it's too late.

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.

Jack, Sydney, Irina, Vaughn and Nadia parachute into Sovogda, Russa to dismantle the giant floating red ball of the Circumfrence which is turning people into mindless, red-eyed zombies out to kill. Back at APO, Marshall and Weiss try use the Blackwell Index to blackmail the Russian defense minister into giving them the access codes to a Russian satellite before the local authorities plan to drop a nuclear bomb on the city to destroy it and prevent the spread of the contagion, and they also discover that Elena is up linking the satellite. In the ruins of the city, a CIA agent, Brodien (the one whom Sydney rescued from Shanghai in the season opener) reminds them that the Rambaldi device is broadcasting a sub audible frequency that physiologically alters people who drink the water-like fluid that has infected the city's water supply and it is irreversible. At the same time, Elena learns of the APO team's arrival and sends Sloane and her men to go out to kill them, leading to a three-way war between Elena's henchman, the APO group, and the zombies leading to Nadia becoming infecting and having a final one-on-one confrontation with Sydney atop a building with the red ball Circumference in the balance.

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.

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.

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.

Rambaldi's catastrophic endgame begins to fall into place as a giant red ball version of the Circumference/Mueller device is found floating over a large city in Russia, driving the citizens mad with violence. After a wounded Dixon reveals that Irina is alive, Sydney, Nadia, and Jack set off to find her. It turns out that Irina had been captured, and then duplicated using Project Helix, in order to give the impression that she was dead. Sydney and Nadia discover Irina being held inside a camp in Tikal, safely in the clutches of Elena's private army. Irina had apparently been working to counter Elena's organization, the Covenant, and actually PREVENT the Rambaldi endgame. Irina is taken to APO and tells them of a page she destroyed, a page that was key to Rambaldi's endgame. Under torture, she finally broke and recreated it for Elena. After a short respite, Sydney, Vaughn, Jack, Nadia, and Irina board a plane parachute down, towards Elena, Sloane, the Circumference....and destiny.