Four years after agents J and K averted an intergalactic disaster J is still working for the MIB while K has returned to the comforts of civilian life. While investigating a seemingly routine crime, J uncovers a diabolical plot masterminded by Serleena, an evil Kylothian monster who disguises herself as a sexy lingerie model. It's a race against the clock as J must find and convince K--who not only has no memory of his time spent with the agency,...

Agent J needs help with his latest case, so he elicits the assistance of Agent K by restoring his memory. Together they battle the latest threat of aliens against Earth.