Sydney Bristow (Jennifer Garner) is a young, athletic, college graduate who was recruited her freshman year as a Secret Agent for SD-6, a top-secret branch of the C.I.A. After a few years, after Sydney confides her lifestyle to her boyfriend, the evil head of SD-6, Arvin Sloane (Ron Rifkin), has him killed. Sydney learns that SD-6 is part of a rogue international agency called the Alliance of 12, out to rule the world. She becomes a double agent, working with the real C.I.A. to bring down SD-6 with the assistance of her handler, Michael Vaughn (Michael Vartan), and her estranged father Jack Bristow (Victor Garber), also a double agent. Along the way, Sydney fights various rival agents, rival terrorist groups, and traitors all the while keeping her cloak-and-dagger lifestyle a secret from her friends