American political action thriller about a disillusioned and obsessed former CIA agent who attempts to assassinate the President of the United States and the Secret Service agent Frank Horrigan who tracks him. Horrigan guarded John F. Kennedy in Dallas at the time of his assassination in 1963, and now is determined to stop the former C.I.A. assassin Mitch Leary at any cost from killing the current President. The agent's nerves are tested to the limit, and nothing seems to be going his way.