Valuable jewels belonging to a japanese exporting company have vanished in Hong Kong. Three different criminal organizations are scurrying about trying to find them, but the only mysterious Suzie Mazuda knows their true whereabouts. A suave HK police detective befriends her to crack the case.
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.