When Boris, an alien who is the last of his race, is confined to a penal colony in space. He escapes and goes to Earth to get the man who placed him there, MIB agent K. He confronts K, K and J corner him but he disappears. J asks K who he is but K doesn't want to say anything. J goes to MIB and learns who Boris is but before he could learn more the one in charge, O, stops him. The next day J goes to pick up K but finds someone else living at his apartment. When he goes to MIB, he looks for K but everyone there tells him, K died in 1969 after tackling with Boris. But J says K captured him. That's when alien vessels which are from Boris' planet show up and they're about to devour the Earth. But J says that K placed a barrier that keeps them from entering Earth in 1969 which would lead to their extinction. It's obvious that Boris went back in time and killed K before he could deploy the barrier. So J goes to see an alien on Earth whose father was also at the penal colony, whom J assumes told Boris that he worked on time travel and his son has the device. J goes to see him and tells him about the invasion. So he sends J back just before K's death. J arrives in 1969 and fails to stop Boris and is captured by the younger K who asks him who he is and what is he doing here. J was told not to tell him anything. But with time running out J tells him but K doesn't believe him at first, so they go out to stop Boris. Only problem J doesn't exactly know what happened so he's not sure where they should go.