He and a group of agents infiltrate the SD-6 office in Los Angeles and take the entire cell hostage with the exception of Sydney and Jack Bristow, who were in the parking garage of the Credit Dauphine building at the time.
He is ultimately released and becomes an agent for the crime syndicate operated by "The Man," later revealed to be Irina Derevko, and he tries to procure a vial of liquid from the vault of SD-6 in order to expose the ink of a document written by Milo Rambaldi.
After Julian Sark and Lauren Reed kill the six leaders of the Covenant cells, they attempt to use this as leverage in order to ascend to more powerful positions within the terrorist organization.
Elena is the sister of Irina and Katya Derevko and was one of the KGB's foremost assassins, responsible for the murder of countless diplomats and politicians throughout Eastern Europe.
Soon Nadia's former caretaker Sophia Vargas arrived in Los Angeles claiming that her reason for coming to the United States was due to an attack by an unidentified group at her home in Lisbon, Portugal.
In order to complete her endgame, Elena, fully aware of the fact that he would at some point double-cross her, also ordered the creation of "Arvin Clone", a corporal in the U.S. Army named Ned Bolger, who was captured and brainwashed to believe that he was, in fact Arvin Sloane, committing numerous criminal acts in the process, such as setting Irina up to appear as if she had contracted an assassin to kill Sydney.
Jack discovered through Katya Derevko that The Covenant was a major terrorist organization set up by Elena in order to secretly acquire Rambaldi artifacts.
Elena, as Sophia Vargas, tells Michael Vaughn the only time she met his father Bill was when he left Nadia in her care at the orphanage in Buenos Aires.
Katya first appeared during the third season, sent by Irina in response to Jack's request for help in extricating Sydney and Vaughn from a North Korean prison.
In the course of searching for The Passenger after her abduction in season 3, Sydney and Vaughn discover video files of Nadia as a small child in an abandoned Russian military bunker, formerly the center of Soviet Rambaldi research.
She is a devout follower of Rambaldi, as evidenced by the eye tattoo on her hand, and as such is one of the many characters obsessed with carrying on the late prophet's work, though her appearances on the show are scant compared to the other zealots.
The first encounter APO personnel had with the transformed Anna occurred in Ghana in the episode "30 Seconds" and resulted in her killing freelance operative Renée Rienne before escaping.
In the following episode ("I See Dead People"), Anna is ordered to intercept the real Sydney, who is en route to contact Michael Vaughn.
In S.O.S, Grace takes part in an APO mission to infiltrate CIA headquarters in Langley, Virginia in order to locate Sydney, who has been kidnapped by Prophet Five.
During the mission, he takes advantage of the opportunity to obtain information from the Witness Protection Program regarding the man who, it is revealed, murdered Grace's wife Amanda.
He first appeared in the first season as the head of an FBI tribunal brought in from Washington DC to interrogate Sydney after she is arrested following evidence linking her to a prophecy by 15th century prophet Milo Rambaldi which suggests she could be a national security risk to the United States.
The character effectively became a second season regular, appearing in almost every episode, although almost nothing was learned about him (to this day his first name remains a mystery) and he was mainly a source of exposition.
Following a raid on SD-6 headquarters, led by McKenas Cole, who says his employer is "The Man", Arvin Sloane seeks a declaration of war by the Alliance of Twelve on Khasinau.
Khasinau arranges for Tippin to be kidnapped by Sark from a CIA safehouse, transported to Taipei and tortured by an evil dentist for more information about the Circumference.
Lauren Reed, an agent of the National Security Council and the wife of Michael Vaughn, was assigned to learn the identity of Lazarey's murderer.
In the third-season episode Legacy, Lee was discovered to have been in charge of the Soviet Union's Rambaldi research in the early 1980s, including overseeing experiments on Sydney's sister Nadia Santos.
He invented a machine code language around 1489, cryptographic algorithms, and sketched the designs of a portable vocal communicator and a prototype that reflected the properties of a transistor.
Rambaldi (1444–1496), an artist, alchemist, engineer, mystic, and renaissance man in the vein of Da Vinci, served as chief architect to Pope Alexander Sextus.
His writings and plans are written in multiple languages ranging from Italian and Demotic hybrids to elusive mixtures of symbols (pre-masonic cipher encryptions).
When FBI Assistant Director Kendall tells Sydney the truth about the two years she was missing, he mentions that she's a celebrity among the Department of Special Research as she was the one to collect the most part of Rambaldi's works.
Irina Derevko recites a similar prophecy at the finale of season 4 that Rambaldi wrote: When Elena Derevko put in motion her scheme to destroy civilization using the contaminated water in conjunction with a giant Mueller device, the team spotted a horse that under the light of the device appeared blood red (which prompted Irina to recite the prophecy); Nadia passed a statue of an angel which had fallen from a building right before she was captured and later becomes infected with the contaminated water.
He then shows Sydney a wall where a drawing similar to the one on page 47 was painted, and gives her an amulet before declaring ominously and prophetically that "it is only a matter of time until the stars fall from the sky, until the end of light".
As revealed in the final three episodes of season four, the first part of Rambaldi's endgame was the Mueller Device (which could be used to change human nature to hatred or peace, depending on the desire of the possessor, as wanted).
However, this was averted when all known Mueller Devices were destroyed and Sloane, the only known beneficiary of The Horizon, was trapped in Rambaldi's own tomb by an explosion, left to exist but never be free for all eternity.
With the downfall of SD-6 and the Alliance, Sloane (now an internationally wanted terrorist) tells Emily they're "free" and leads her to believe he has finally left behind his deceptions.