Anthony Geiger was appointed as acting head of SD-6 after the defection of Arvin Sloane. (The Getaway).

Before Season 2[]

Geiger has a mysterious past. Agent Kendall admits that the CIA, nor any other institution in the United States, has any information on him. Sark claimed in conversation with Sydney, that his background is West German intelligence, while in the late 80's he worked with Jack Bristow on an unspecified mission.

Season 2[]

Following Geiger's appointment, he was quick to set out in tying the loose ends that Sloane had left. In the process he discovered that both Jack and Sydney were double agents due to an e-mail that Sloane left behind. Jack was immediately apprehended by Geiger, where he was tortured by electroshock in an attempt to reveal his loyalties.

Geiger was shot dead by Sydney, during the CIA's global hostile takeover of Alliance cells. (Phase One).