An experienced agent from a secret organization that polices extraterrestrial interactions on Earth, known as the Men in Black (MIB), tracks down an alien criminal, leading to an incident that reveals the alien's violent intentions. Recognizing the threat, he decides to recruit a new partner to bolster the agency's ranks. His choice is a wise-cracking, street-smart NYPD officer who chases down a suspect with unusually agile abilities. After showcasing his skills, the officer is recruited and undergoes a life-altering transformation, forsaking his identity and becoming Agent J, the newest member of the enigmatic agency.

Together, the veteran agent, now known as Agent K, and the rookie Agent J embark on a mission to thwart an intergalactic disaster. As they delve deeper into their investigation, they uncover a plot that endangers the Earth. The new partners must track down a device that is critical to the survival of the planet. Struggling to stay inconspicuous in a city teeming with unsuspecting humans and disguised aliens, the agents navigate a complex alien underworld with only their wits and an arsenal of advanced technology provided by MIB. They must work against the clock, as the fate of the planet hangs in the balance, testing their new partnership and the secretive agency's ability to protect Earth from the scum of the universe.