After a scrape with a few hot-heads on the subway, homeless man and former government agent John Reese is offered a job by the somewhat secretive Mr. Finch. After 9/11, Finch developed a computer program that would sift enormous amounts of information, looking for patterns of behavior or activity that would predict another attack. It also provided information about individuals who could be in danger. Finch wants to do something about those people. The first on his list is Diane Hanson, an Assistant District Attorney currently working on a major prosecution. Reese agrees to help out and begins by watching her. It all leads to an unexpected conclusion.