When Jack was a child, his parents had him genetically enhanced. The procedure increased his intelligence and physical abilities, but left him as a violent, aggressive, paranoid and anti-social person. Jack's parents admitted what they had done for Jack to get treatment. Jack would later become a patient of the Institute and was kept with other genetically enhanced people. (DS9 episode: "Statistical Probabilities")
By the 2370s, Jack had been selected by Karen Loews (along with Lauren, Sarina Douglas and Patrick) to be separated from the Institute's other residents so she could work with him and help give him a normal life.
In 2374, Doctor Loews brought Jack and the others to Deep Space 9 for Julian Bashir to work with him. It was hoped that Bashir, as someone who had been genetically enhanced but had led a normal life, would be able to convince him he could do the same.
Jack and the others would later watch a speech of Corat Damar's and deduced exactly how he came to power. Benjamin Sisko was able to convince Starfleet to give them access to Starfleet's data on the Dominion and the war. Working with Bashir, Jack and the others deduced the war was unwinnable and that surrender was the Federation's only option. After Starfleet refused to accept their data, Jack and the others tried to pass the classified information on Starfleet's battle plans and fleet deployments to Damar and Weyoun, but were stopped after Sarina informed Bashir of their plan. Jack and the others were returned to the Institute, with Jack planning to find a way to beat the Dominion. (DS9 episode: "Statistical Probabilities")
In 2375, Jack and the others returned to Deep Space 9 on the USS Farragut, posing as Starfleet officers, for Sarina to undergo the procedure to free her from her catatonic state. At the same time, Jack, Patrick and Lauren were concerned that the universe had too much matter and would collapse in sixty or seventy trillion years. (DS9 episode: "Chrysalis")
Around this time, Jack visited Elim Garak's shop and told him he planned to persuade Starfleet to elevate Bashir to the command of the station, feeling a genetically enhanced person should be leading the station during the war. Jack and the others petitioned the Federation Council, but no one took them seriously. (DS9 novel: A Stitch in Time)
In 2376, the Section 31 agent Cole told Bashir that many genetically enhanced people living in the Federation would consider Jack to be a "social butterfly" compared to them. Cole also predicted that if the rogue genetically engineered 31 agent Ethan Locken started a war, Starfleet would abandon Jack and the others. (DS9 - Section 31 novel: Abyss)
Later that year, having been affected by the cathedral/anathema artifact, Bashir experienced a vision where he was placed in a cell with Jack and the others. In the vision, Jack helped Bashir to escape. (DS9 - Mission Gamma novel: Cathedral)
- DS9 episode: "Statistical Probabilities"
- DS9 episode: "Chrysalis"
- DS9 short story: "Signal to Noise"
- ST - Typhon Pact novel: Zero Sum Game