The story takes place four years after the first film. At this time, special police officer K (Tom Lee Jones) has retired and become an ordinary postmaster, while J (Will Smith) continues to work for MIB. The evil queen of Carlosser, Serpentina, came to Earth to find the cosmic energy "Star of Sata" and occupied the headquarters of MIB. The Princess of Sata, Rona, who fled to Earth, once asked MIB to hide the "Star of Sata" on Earth. K, who was fully responsible for this matter, refused her for the safety of the Earth. Faced with the menacing Serpentina, MIB sent J to find K and investigate the truth of the incident. How to convince K, who has lost his memory, to believe in the existence of aliens has become the first problem J faces...