In present-day America, Tommy Lee Jones plays Agent K, a member of an organization that has been keeping track of extra-terrestrial aliens on Earth for over 40 years. When K finds himself in need of a new partner, a brash NYPD detective, James Edwards (Will Smith) fills the position, becoming Agent J. Armed with space-age technology (which J barely understands) and their razor-sharp wits, J and K investigate a newcomer (played by Vincent D'Onofrio) who is bad news for Earth.