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.
In a final effort to stop Sloane, Jack sacrificed his own life to trap an immortalized Sloane in a cave for the rest of eternity.
- ID-CLASS: USS-CI-2300682
- Present Location: Los Angeles
- Place Of Birth: London, Ontario, Canada
- Height: 6'2"
- Weight: 195
- Characteristics: Left-handed
- Training/Special Skills: Physics, Aeronautics, Engineering, Game Theory, Cryptology, Linguistics.
- Languages: English, Chinese, Arabic, Russian, Spanish, Czech
- Education: Doctorate, LAS.
Jack kept his affiliation with SD-6 a secret from Sydney, who also worked there. His cover was that he worked in supplying airplane parts. Jack was one of the few people working at SD-6 who knew its true allegiance; that it was a branch of the Alliance of Twelve, and he was working with the real CIA against SD-6 (Truth Be Told).
Shortly before Season 1, Daniel Hecht called Jack to ask for his daughter's hand in marriage. Jack was shocked that Daniel would ask as he clearly did not know his daughter very well, but accepted (Truth Be Told).
Working as a CIA mole in SD-6
Jack was informed that Sydney had told Danny that she worked for SD-6, and so he was tasked with killing Danny to prevent a leak of information regarding their agency. After Danny's death, Sydney attended the funeral and Jack observed from his car. He then found out that Sydney was being targeted by Sloane because she was a potential threat and managed to save her from some attacking agents. He explained that he also worked for SD-6, and said that SD-6 was part of the Alliance of Twelve, a criminal organization, and not the CIA as she had been led to believe. He tried to get to Switzerland, but she refused and ran away. He later went and told her that her request to be a double agent for the CIA had been approved, and informed her that he was also one working against SD-6 (Truth Be Told).
Sydney met with her father at SD-6, who said that it would facilitate their plan if Sloane knew that she knew that Jack worked at SD-6. Sydney asked if he knew that they were going to kill Danny. He said that he did, and she slapped him. Sydney told him never to speak to her again, then left. He later told her that he booked a flight for Danny to go to Singapore but he arrived too late; he had already been killed. Jack told Sloane that Sydney had gone away for a few days, when in fact she had gone to get a nuclear weapon back that SD-6 had sold to terrorists (So It Begins).
Working at the CIA
Working for APO
Laura Bristow (aka Irina Derevko)
- Jack Bristow: Sometimes a satisfying lie, Sydney, can do more good than the awful truth. (The Awful Truth).