James Bond, after his last mission, is on vacation! However, his handler nonetheless tells him to spy on a fellow guest at his hotel! He sees Goldfinger, a gold-bullion merchant or trader of some kind, cheating at some sort of betting card game! Bond blackmails him into losing on purpose and then seduces his employee! However! The next morning he's knocked out by Goldfinger's manservant, and wakes to find Jill dead and also painted gold! She is supposedly dead because of having been painted gold, though it's unclear this medically follows.
The scene skips to London, where Bond learns that Goldfinger is somehow smuggling gold across country borders in order to profit from selling it internationally! He is tasked with finding out how. This involves meeting Goldfinger at his country club (some sort of retreat where rich people spend time) and playing a game called golf with him, also with a bet made.
More things happen. Many more characters are introduced. A nuclear physicist from a faraway country called China is involved, and Bond discovers that Goldfinger plans to release toxic gas to kill everyone in the US gold-bullion vault. There is also a bomb involved. Bond and some others are locked into the gold vault! There is a dramatic showdown where multiple people attempt to defuse the bomb and Goldfinger's manservant fights them; Bond wins but is still unable to disarm the mechanism, until seconds before the countdown runs out, an atomic specialist is rushed in and...flips the off switch on the device.
This seems like the climax, really, but the movie inexplicably ends with Bond being flown to have lunch with the US President, which is interrupted by Goldfinger hijacking the plane! However, when in the struggle his gun accidentally fires at a window, the pressure difference sucks him out the broken window! The plane crashes into the sea but Bond and the pilot parachute down to safety. And then hide from search helicopters??? The reason why is unclear and the movie ends there.