After breaking out of LunarMax, a moon-based maximum security
prison, Boris the Animal (Jemaine Clement) decides to go back in time
and eliminate the person who arrested him - Agent K (Josh Brolin). When
he does so, Agent J (Will Smith) realizes that the timeline has been
changed and he too travels back to July 15, 1969, the day before Agent K
is killed. After overcoming some disbelief, J manages to convince young
K and others of just who he is and why he's there. With the help of
Griffin (Michael Stuhlbarg), a being who can see all timelines, they
track Boris down. J also learns a secret, something old Agent K (Tommy
Lee Jones) had never told him.