Harold Finch, a billionaire software-genius, creates a machine for the government designed to detect acts of terror before they happen, by monitoring the entire world through every cellphone, email and surveillance camera. Finch discovered that the machine sees everything, potential terrorist acts and violent crimes that involve ordinary people. When the government considered violent crimes between normal people "irrelevant", Finch built a back door into the system that gives him the social security number of a person involved in a future violent crime so he could act. Partnered with John Reese, an ex-CIA agent, the two work in secret to prevent violent crimes before they can happen.