Alien refugees live in secret on Earth, disguised as humans. Men in Black is a secret agency that polices these aliens, protects the Earth from intergalactic threats and uses memory-erasing neuralyzers to keep alien activity a secret from the public. Men in Black agents have all traces of their former identities erased and retired agents are neuralyzed and given new identities.
NYPD officer James Darrell Edwards III pursues a supernaturally fast and agile suspect in New York City. Men in Black agent K interviews James about his encounter, then neuralyzes him and leaves him a business card with an address. Edwards goes to the address and undergoes a series of tests, for which he finds unusual solutions. While the other candidates are neuralyzed, K offers Edwards a position with the Men in Black. Edwards accepts and his identity is erased, becoming Agent J, the newest Men in Black recruit.
In upstate New York, an alien crash-lands and kills a farmer named Edgar to use his skin as a disguise. The alien goes into a New York restaurant and kills two aliens disguised as humans. He steals from them a container, searching for something, but finds only diamonds inside. After investigating the crash landing at the farm, K concludes that Edgar's skin was taken by a "bug", a species of aggressive cockroach-like aliens. He and J head to a morgue to examine the bodies the bug killed. Inside one body they discover a dying Arquillian alien, who says that "the galaxy is on Orion's belt". The alien, who used the name Rosenberg, was a member of the Arquillian royal family. K fears his death may spark war.
Men in Black informant Frank the Pug, an alien disguised as a dog, explains that the missing galaxy is a massive energy source housed in a small jewel. J deduces that the galaxy is hanging on the collar of Rosenberg's cat Orion, which refuses to leave the body at the morgue. J and K arrive just as the bug takes the galaxy and kidnaps the coroner, Laurel Weaver. The Arquillians deliver an ultimatum to Men in Black: return the galaxy within an hour or they will destroy Earth.
The bug arrives at the observation towers of the New York State Pavilion at Flushing Meadows, which disguise two flying saucers, and abandons Laurel. It escapes on one saucer, but K and J shoot it down. The bug sheds Edgar's skin and swallows J and K's guns. K provokes it until he too is swallowed. The bug tries to escape on the other ship, but J slows it down by taunting it and crushing cockroaches, angering it. K blows the bug apart from the inside, having found his gun inside its stomach. J and K recover the galaxy and are about to be attacked by the bug again but Laurel shoots it with J's gun.
At Men in Black headquarters, K tells J that he has not been training him as a partner but a replacement. At K's request, J neuralyzes him; K returns to his civilian life and Laurel becomes J's new partner, L.
Who does the Men In Black protect the Earth from ?
intergalactic threats