Alias is an American spy action thriller television series created by J. J. Abrams that was broadcast on ABC for five seasons from September 30, 2001, to May 22, 2006. It stars Jennifer Garner as Sydney Bristow, a double agent for the Central Intelligence Agency posing as an operative for SD-6, a worldwide criminal and espionage organization. Main co-stars throughout all five seasons included Michael Vartan as Michael Vaughn, Ron Rifkin as Arvin Sloane, and Victor Garber as Jack Bristow.

The first two seasons of Alias mainly explore Sydney's obligation to hide her true career from her friends and family as she assumes multiple aliases to carry out missions as well as her efforts to take down SD-6 with the help of the CIA. The series' later seasons deal with multiple character and plot-driven storylines, with a recurring focus on the search for and recovery of artifacts created by Milo Rambaldi, a fictitious Renaissance-era figure with similarities to both Leonardo da Vinci and Nostradamus.

Alias was well received among critics and has been included in several "best of" lists, including the American Film Institute's top ten list for television programs in 2003. The series also received numerous awards and nominations. Alias is considered to be part of a wave of television series from the late 1990s and early 2000s that feature strong female characters, alongside Buffy the Vampire Slayer, Xena: Warrior Princess, La Femme Nikita, and Dark Angel.

Plot

Season 1 (2001–02)

Seven years before the first episode, Sydney Bristow was an undergraduate student. She was approached by someone who claimed to work for the Central Intelligence Agency and offered her a job as an agent. Having accepted, she was assigned to a unit called SD-6, which she was told was a secret "Black Ops" section of the CIA. She became a field agent. In the pilot, she tells her fiancé Danny Hecht (played by Edward Atterton) that she is a spy and as a result of her revealing SD-6's existence to him, Danny is murdered by SD-6. She discovers that her father Jack Bristow is also an SD-6 agent and that SD-6 is not part of the CIA; instead, it is part of the Alliance of Twelve, an organization that is an enemy to the United States. Sydney decides to offer her services to the real CIA as a double agent. Having learned that her father is also a double agent for the CIA, she begins the long and arduous task of destroying SD-6 from the inside.

Major plotlines from season 1 include Sydney hiding her triple identity from her friends, both in her personal life and in her SD-6 job, Will Tippin's investigation into Danny's death, the race to find Milo Rambaldi (a 15th century philosopher with an uncanny understanding of the future) artifacts, and the past activities of Sydney's mother. Sub-plots include Sydney's friendship with Francie, Francie's romantic relationship with Charlie, and Sydney's developing relationship with her CIA handler Michael Vaughn, of whom she is skeptical at first but grows to trust as her life becomes increasingly stressful. Season One focuses on the development of Sydney's character and allows the audience to become familiar with her.

Season 2 (2002–03)

The second season begins with the introduction of Irina Derevko, Sydney's mother, who soon becomes a key character in the series. Midway through the second season, the series underwent a "reboot" of sorts with Sydney successfully destroying SD-6 and becoming a regular agent for the CIA, still in pursuit of former SD-6 leader Arvin Sloane, his associate Julian Sark, and the Rambaldi artifacts. Sydney's friends at SD-6, Marcus Dixon and Marshall Flinkman, are finally made aware of her dual identity and recruited into the CIA. Sydney also begins a romantic relationship with Vaughn, now that their relationship will not endanger them.

In the second half of the season, it is revealed that Francie Calfo, Sydney's best friend, was murdered and replaced by Allison Doren, a woman who was transfigured to look exactly like her. Allison was then in a position to spy on Sydney and Will. The end of the season saw Will possibly murdered and Sydney killing Allison and then falling unconscious. Sydney awakens two years later in Hong Kong, unable to remember the two years that have passed. She soon learns that her friends and the CIA believed her to be dead, and Vaughn found a new love and is now married.

Season 3 (2003–04)

The third season takes place two years after the events of season 2, with Sydney having been missing and presumed dead. DNA evidence in a badly burned body confirmed her death to her family and friends. The truth, however, is that Sydney was kidnapped by a terrorist organization called The Covenant, who tried to brainwash her into believing she was an assassin named Julia Thorne. Eventually Sydney voluntarily had her memories of the two years erased in an attempt to forget some of the deeds she was forced to undertake as Julia and to ensure that one of Rambaldi's most dangerous artifacts would never be found.

As Sydney recovers, she begins investigating her absence while reintegrating into the CIA. There she deals with the facts that Arvin Sloane had become a world-renowned humanitarian after being pardoned, and that Michael Vaughn had married NSC agent Lauren Reed. Reed is later revealed to be a member of the Covenant and a lover of Julian Sark. The National Security Council plays a role as a government organization that holds massive unsupervised power, with a Guantanamo-like detention facility, considerable influence over the CIA, and driven by questionable motives. Sydney later discovers that her mother and Arvin Sloane had a child together, the result of an affair between the two years before Sydney's birth. She locates her half-sister, Nadia, and rescues her from being killed by the Covenant. At the end of the season, Sydney goes on a mission and encounters Lauren. After they battle, Lauren begins to taunt Sydney by saying she has information about her past. When Vaughn shows up, Sydney goes to him, leaving Lauren a chance to attack again. Vaughn shoots Lauren, and she dies, but before she does, she gives Sydney the number of a security deposit box where she can find information about her past.

Season 4 (2005)

Season 4 begins where season three ended: with Sydney uncovering a shocking, classified document called "S.A.B. 47 Project." It is explained that the document authorizes Jack Bristow to execute Sydney's mother, who mysteriously placed a contract on Sydney's life (this was apparently something of a retcon to cover for actress Lena Olin presumably not returning to the series). The first page refers to Sydney as the "active" subject of a "project" that began on April 17, 1975, a possible reference to Project Christmas, and also setting up Jack as either the real head of (or somehow involved with) the Covenant and/or being a descendant of Rambaldi or Rambaldi himself. Sydney joins a black ops division of the CIA, patterned after SD-6 and run by her one-time nemesis Arvin Sloane. The new division is dubbed "APO": Authorized Personnel Only. Members of APO (all hand-picked by Sloane) include almost all of the recurring characters from previous seasons, including Jack, Vaughn, Sydney's former partner (and third-season CIA director) Marcus Dixon, the computer and technical genius, Marshall Flinkman, and Vaughn's best friend Eric Weiss (brought in after having to be rescued by Sydney and Vaughn, who he previously believed to have left the CIA). Sloane's daughter and Sydney's half-sister Nadia Santos also eventually returns to join APO.

During the season, an Arvin Sloane impostor, jokingly identified as "Arvin Clone", acquired the technology to implement a Rambaldi-predicted apocalypse. Using Omnifam, the real Sloane had polluted the world's drinking water with chemicals that caused feelings of peace and tranquility. However, these feelings can be reversed with the Mueller device. The third Derevko sister, Elena, had built a giant Mueller device in Sovogda, Russia, which drove the residents to insanity. Sydney, Jack, Irina, Nadia, and Vaughn parachute in, destroy the device and kill Elena. But Nadia is injected with the tainted water and driven insane. She battles Sydney until Sloane is forced to shoot his own daughter. Nadia is later put into a coma while a cure is sought, and Irina is allowed to escape. The season concludes with Sydney and Vaughn becoming engaged. On a trip to Santa Barbara, Vaughn confides a shocking secret: his name isn't really Michael Vaughn; their initial meeting wasn't coincidental; and that his allegiance may not be to the CIA. Before he can divulge any more information, another car crashes into theirs and the season ends.

Season 5 (2005–06)

As season five begins, Vaughn is abducted. Sydney learns that Vaughn is under suspicion of being a double agent and that the crash may have been a cover for his extraction. Vaughn later escapes and explains to Sydney that his real name is André Michaux. He reveals that he is investigating a secret operation known as Prophet Five, which at one point involved his father. During a mission in recovering a Prophet Five book, Sydney receives a phone call from her doctor with some untimely news – she's pregnant. (This development was created to deal with the actress' real-life pregnancy.Gary Susman.Morning Sickness Becomes Elektra: Is Jennifer Garner pregnant? E! says sources confirm she's expecting a little Affleck," Entertainment Weekly, May 9, 2005.Jennifer Garner & Sydney Bristow Will Both Be Pregnant , Entertainment Tonight, July 27, 2005.) Vaughn is later shot, and apparently killed, on orders of Prophet Five operative Gordon Dean. Four months later, as Sydney continues to investigate Vaughn's murder, she works with an assassin and associate of his, Renée Rienne, in order to unearth the inner workings of Prophet Five, while at the same time trailing Dean and his criminal organization "The Shed", disguised as a black ops CIA division, very much like SD-6.

Two new members are added to APO to replace Weiss, who moved to Washington, D.C. for a new job, and Nadia, who is still in a coma. Thomas Grace is a brash young agent with unorthodox methods who often butts heads with Sydney. Rachel Gibson is a computer specialist who, like Sydney, was deceived into thinking she was working for the real CIA and briefly works as a mole within The Shed, as did Sydney within SD-6, before The Shed's destruction by Dean. Sydney's mom and dad help her deliver her baby girl while under attack in a high-rise in Vancouver, Canada, on a mission in season 5, episode 11: "Maternal Instinct." Shortly afterwards, it's finally revealed that Vaughn is alive—living and hiding in Nepal. In an ongoing subplot, Arvin Sloane follows his own personal obsession, finding a cure for Nadia. Sloane is jailed for his actions during Season 4; however, he is released after the sentencing committee is manipulated by Dean. In exchange for his freedom, Sloane is now working for Dean as a mole within APO. Unaware of Sloane's new allegiance, Jack agrees to let Sloane rejoin APO and use its resources to seek a cure for his daughter.