Lakonan Will Smith memang best as usual bersama mimik mukanya, tak pernah menghampakan. bila menonton movie ni, don't be so serious ye, ala citer alian + lawak + organisasi lelaki bersut hitam macam upacara funeral je...of course kena gelak sokmo. meh layan sinopsis dan trailer, lepas ni korang g menonton okay ;)
Agent O (Emma Thompson), the new Chief deduces from J's statements that a fracture has occurred in the space-time continuum. The two realize Boris must have time-jumped to 1969 and killed K, resulting in an imminent invasion of Earth by his race, the Boglodites, due to the absence of the protective ArcNet shield around Earth, installed by K in 1969. Aided by electronic-shop owner Jeffrey Price, son of Boris' fellow prisoner Obadiah Price, who created the time-travel device, J time-jumps off the Chrysler Building to reach time-travel velocity (Jeffrey also cryptically, though excitedly, informing J that the reason he remembers K where nobody else can is because he was 'there'). With only 24 hours to stop Boris, J arrives a day before Boris kills K.
J follows a clue to Coney Island, where 29-year-old junior agent K (Josh Brolin) arrests him and then questions him at MIB headquarters, while a young Agent O (Alice Eve) and Chief X come by. Getting no answers, K decides to place J in a large, primitive Neuralyzer. At the last second, J says he'll tell the truth of his mission and that he is from the future. As a team, they follow Boris' trail to a bowling alley and then to The Factory, the studio / party space of Andy Warhol's (Bill Hader), who is actually the undercover Agent W. The Agents meet the alien Griffin (Michael Stuhlbarg), an Arcadian who possesses the ArcNet and is able to see all possible futures. Griffin leaves before Boris arrives to snatch him. The Agents locate Griffin at Shea Stadium, where he gives them the ArcNet and instructs them to place it onto the Apollo 11 lunar rocket launch occurring in less than six hours. Boris then snatches Griffin, but the agents, on monocycles, give chase and recover Griffin.
Upon arriving at Cape Canaveral, the agents and Griffin are arrested by military police. A Colonel (Mike Colter), however, allows the agents to carry on their mission after Griffin uses his precognitive power to show him what J and K will accomplish. J uses the time-jump device to confuse future Boris- allowing Boris to shoot him before jumping back in time so that he can attack Boris again while avoiding the alien's attacks-, and pushes him off the pad. K, battling the current Boris, shoots Boris' left arm, causing him to fall back to the ground. K plants the ArcNet on the rocket, and the protective shield deploys after leaving Earth's atmosphere, the launch sequence destroying the future Boris. The Colonel congratulates K, who invites him to join the agency.
As J watches from the distance, however, 1969 Boris emerges from the blast chamber and kills the Colonel, only to be killed by K. A child named James exits a military vehicle looking for his father. He pulls out a pocket watch, revealed earlier to have been passed down to Agent J by his father, and J realizes that the colonel killed by Boris was actually his father. K neuralyzes young James, telling him his father was a hero, thus fulfilling the 'prediction' that J would be present at the moment history changed.
J returns to the present day, where he meets his partner at the usual diner. There, he shows K his father's pocket watch. The senior agent, in return, tells him it was an honor to have met him that fateful day. As they leave the diner, Griffin, a few seats away, muses all is well with the world (breaking the fourth wall in the process and revealing to the audience that his powers of observation also make him aware of the real world moviegoers), except for the fact that K forgot to leave a tip, indicating they are in a timeline where the Earth is about to be hit by an asteroid. Then, K returns to the diner and leaves a tip, revealing this timeline to be one where the asteroid disintegrates when hitting a satellite, and the film ends.