Jack was brought into the King Mob's Invisibles cell in order to replace John-A-Dreams in the role of Spirit. After being liberated from Harmony House (a new juvenile detention center run by the Outer Church) by King Mob, Jack spent some time on the streets of London, where both sides tried to recruit him, often in the garb of their opponents (Kate, looking like a stereotypical punk, while "our cell" looks like Sir Miles on a "fox hunt" and Mister Six poses as a member of the establishment in his "Big Malkie" identity). However, it was under the tutelage of Tom O'Bedlam that Jack begins to learn what it is to become Invisible.
While in America, Jack began a relationship with Boy, which is on hold currently due to her leaving the Invisibles and Jack being trained by Elfayed. He and Fanny have also struck up a friendship after dancing for the Harlequinade to get the Hand of Glory.
To many, Jack is the central character in The Invisibles. There is a distinct possibility that he is the future Buddha and that the detonation of his soul in 2012 will bring about the Eschaton. But for now, he is a foul mouthed hard ass who deconstructs everyone's preconceived notions about what it means to be Invisible.