While I wouldn't recommend that: (spoilers ahead) >!Harold Finch (Michael Emerson) created a Machine after 9/11 that would use all cameras, the internet, and phones/texts to learn about people and help prevent terror attacks. He recruits an ex-CIA agent John Reese (Jim Caviezel) to help him out. For most of the show they get social security numbers of people in New York who might be the victim or the perpetrator of a crime and have to determine which one a person of interest is and stop the crime from happening. Eventually Lionel Fusco (Kevin Chapman), Root (Amy Acker), and Sameen Shaw (Sarah Shahi) join them in their endeavors. Along the way, a second AI, Samaritan, is activated and has the same capabilities of The Machine, but without the moral compass Harold was able to program in, so it's essentially a ruthless, evil AI.!<

I've missed out on some other plotlines, but for this specific episode that's probably all that's necessary