Joel Barish, heartbroken that his girlfriend underwent a procedure to erase him from her memory, decides to do the same. However, as he watches his memories of her fade away, he realises that he still loves her, and may be too late to correct his mistake.
Kay and Jay reunite to provide our best, last and only line of defense against a sinister seductress who levels the toughest challenge yet to the MIB's untarnished mission statement – protecting Earth from the scum of the universe. It's been four years since the alien-seeking agents averted an intergalactic disaster of epic proportions. Now it's a race against the clock as Jay must convince Kay – who not only has absolutely no memory of his time spent with the MIB, but is also the only living person left with the expertise to save the galaxy – to reunite with the MIB before the earth submits to ultimate destruction.
Shy, straight-A student Ellie is hired by sweet but inarticulate jock Paul, who needs help wooing the most popular girl in school. But their new and unlikely friendship gets tricky when Ellie discovers she has feelings for the same girl.
