Jonathan "Jack" Donahue Bristow was the father of Sydney Bristow and a fellow double agent for the CIA at SD-6. He assisted his daughter in bringing down the criminal organization and assisted the CIA at their base of operations in Los Angeles thereafter. He was recruited to APO, a black ops division of the CIA, by former superior at SD-6 Arvin Sloane, who ultimately betrayed the U.S. government in pursuit of the findings of Milo Rambaldi. Jack was left in charge of APO after this.