I know what you're thinking.
'Oh, it's the 3rd film, can't be any good.'
You're wrong. I'm sorry, Common Sense, but this is the third AND best film in the series, and doesn't lack anything.
This film is about James, or Agent J years after the story in the second film.
He goes on a quest to find his retired partner, Agent K, and soon finds him working in a post office, with no memory whatsoever of his Men In Black career. He then finds out that the villain, Boris the Animal has escaped from his prison. After he does some research on the MIB database, he finds out that in the year 1969, Agent K sent Boris to prison, rather than killing him.
So, he goes back in time and uses a young Agent K to reset the events from that year, so he can kill Boris rather than send him to prison.
MIB 3 has a great plotline, and you just can't reject the fantastic concept of Time travel. I'm rating it 5 out of 5 stars, and I hope I have convinced you to go see it!