Ben is placed in harm's way by someone who he thought he could trust. And when the 2nd Mass are trapped in the basement, the situation takes a turn for the worst.

Agent J must travel back in time to MIB's early years in the 1960s and save his partner, Agent K, from being assassinated by an alien. Along the way, Agent J teams up with young Agent K and learns that there are secrets to the universe that Agent K never told him.

There's trouble brewing in peaceful Glenview, Ohio. That's why four civic-minded citizens, armed with flashlights, walkie-talkies and spiffy new jackets, have teamed up to safeguard their community. But the guys find more than they bargained for when they uncover an alien plot to destroy Earth, and now these bumbling heroes are Glenview's only chance to save the neighborhood and the world from annihilation.