John Reese, a presumed dead former CIA agent who is approached by a mysterious billionaire named Harold Finch to prevent violent crimes before they happen by using an advanced surveillance system dubbed "The Machine". Their unique brand of vigilante justice attracts the attention of two NYPD officers, Joss Carter and Lionel Fusco, whom Reese uses to his advantage as he investigates persons of interest. Reese and Finch are later aided by Samantha "Root" Groves , a highly intelligent computer hacker and contract killer who the Machine later identifies as its "analog interface" and Sameen Shaw, a former ISA assassin who unknowingly dealt with the "relevant" numbers found by the Machine.