An undercover cop finds that the line between his own personality and that of the character he's created have begun to dangerously blur in this drama. John (Reece Dinsdale) is a British police detective whose skill is matched only by his arrogance.
Acts of brutal hooliganism have become commonplace at the football matches featuring one of London's minor league teams, Shadwell Town, and the police suspect that there is a more criminal undercurrent to these actions than merely fandom gone wrong after a few pints of beer.
So John is made part of an undercover team along with Trevor (Richard Graham) and two other officers; they are to blend in with the most rabid fans and learn what is behind the violence.
John also makes the acquaintance of Lydia (Saskia Reeves), a barmaid at a pub where many of the hooligans hang out, he and becomes friendly with her as a way of obtaining more information.
But as John sinks deeper into a life of alcohol and violence while hanging out with the Shadwell Town hooligans, he finds he likes it more and more, and in time, he finds that he's becoming one of the brutal thugs he set out to capture.
He also finds his relationship with Lydia is no longer just a matter of business, much to the chagrin of his wife Marie (Claire Skinner). I.D. marked the feature debut for British director Philip Davis, who also directed several distinguished productions for U.K. television.