It's summer in Graviton City, and the girls all have a break from school! A-Ko decides to lose a few inches, C-Ko makes a list of all the cool things that she'll buy, and B-Ko vows to get A-Ko out of the way once and for all so that she can have C-Ko to herself. To this end, she designs a new giant mecha, better than all the others. But her father steals her designs and uses them to attack the crashed alien spacecraft (now high-class restaurant) in an attempt to steal the advanced technology of the aliens.
Veteran buttoned-down LAPD detective Roger Murtaugh is partnered with unhinged cop Martin Riggs, who -- distraught after his wife's death -- has a death wish and takes unnecessary risks with criminals at every turn.
Test pilot Tuck Pendleton volunteers to test a special vessel for a miniaturization experiment. Accidentally injected into a neurotic hypochondriac, Jack Putter, Tuck must convince Jack to find his ex-girlfriend, Lydia Maxwell, to help him extract Tuck and his ship and re-enlarge them before his oxygen runs out.
Navy Lt. Tom Farrell meets a young woman, Susan Atwell , and they share a passionate fling. Farrell then finds out that his superior, Defense Secretary David Brice, is also romantically involved with Atwell.