Alias - Season 4 - Eps 20: The Descent
After a tactical group infiltrates the DSR and steals Rambaldi artifacts, CIA director Hayden Chase discovers that the alarms at the DSR were disabled from Nadia's computer, allowing the raid to happen, and shows up at the apartment to question her. Soon Sloane and Jack arrive and suspect that Sophia, who had access to the computer while she was living with Syd and Nadia, is Elena Derevko. They follow her trail to a dead Rambaldi follower, a stunning betrayal, and a presumed dead family member...
About Alias

Title: Alias
First Air Date: 2001-09-30
Last Air Date: 2006-05-22
Status: Ended
Rating: 6.736/10 (from 645 votes)
Language: EN
Seasons: 6
Total Episodes: 105
Network: ABC
Genres: Action & Adventure, Drama
Production Companies: Bad Robot, Touchstone Television
Synopsis
Sydney Bristow, an agent who has been tricked to believe she is working for the U.S. government, is actually working for a criminal organization named the Alliance of Twelve. Upon learning this, Sydney becomes a double agent for the real CIA.
Cast

Jennifer Garner
Sydney Bristow

Michael Vartan
Michael Vaughn

Victor Garber
Jack Bristow

Ron Rifkin
Arvin Sloane

Carl Lumbly
Marcus Dixon

Kevin Weisman
Marshall Flinkman

Rachel Nichols
Rachel Gibson

Amy Acker
Kelly Peyton