Plot

James Bond (Sean Connery)-agent 007-pursues Ernst Stavro Blofeld (Charles Gray) and eventually finds him at a facility where Blofeld look-alike are being created through surgery. Bond kills a test subject, and later the "real" Blofeld, by drowning him in a pool of super-heated mud.

While assassins Mr. Wint (Bruce Glover) and Mr. Kidd (Putter Smith) systematically kill several diamond smugglers (and acquire their cache of diamonds in the process), M (Bernard Lee) suspects South African diamonds are being stockpiled to depress prices by dumping (80% of diamond supplies come from South Africa), and orders Bond to uncover the smuggling ring (persuaded by Sir Donald Munger (Laurence Naismith) A diamond expert who brings the case to MI6). Posing as professional smuggler and assassin Peter Franks, Bond travels to Amsterdam to meet contact Tiffany Case (Jill St. John), a diamond smuggler. The real Franks shows up, but Bond intercepts and kills him, and switches IDs to make it seem like Franks is Bond. Case and Bond then go to Los Angeles, smuggling the diamonds inside Franks' corpse. Q (Desmond Llewelyn), Head of MI6's technical department. Miss Moneypenny (Lois Maxwell), M's secretary.

At the airport Bond meets his CIA ally Felix Leiter (Norman Burton) (who clears the shipment from customs), then travels to Las Vegas. At a funeral home, Franks' body is cremated and the diamonds passed on to another smuggler, Shady Tree (Leonard Barr). Bond is nearly killed by Wint and Kidd (who had followed him and Tiffany from Amsterdam on their flight) when they put him in a casket to be burned in a cremation retort, but Tree stops the process when he discovers that the diamonds in Franks' body were fakes. Shady wants Franks/Bond to deliver the real diamonds, but Franks/Bond says that he was promised $50K for the delivery and wants his money.

Bond tells Leiter to ship him the real diamonds. Bond then goes to the Whyte House, a casino-hotel owned by the reclusive billionaire Willard Whyte (Jimmy Dean), where Tree works as a stand-up comedian. Bond discovers there that Tree has been killed by Wint and Kidd, who did not know that the diamonds were fake. Wint & Kidd suspect that Franks/Bond has the real diamonds. At the craps table Bond meets the opportunistic Plenty O'Toole (Lana Wood), and after gambling, brings her to his room. Gang members ambush them, throwing O'Toole out of the window and into the pool. Bond spends the rest of the night with Tiffany Case (who offers Franks/Bond a deal to deliver the diamonds and she promises him a 50-50 split and a passage out of Las Vegas), instructing her to retrieve the real diamonds at the Circus Circus casino.

Tiffany reneges on her deal to meet back with Bond and instead flees, passing off the diamonds to the next smuggler. However Franks/Bond confronts her at her apartment in Las Vegas, seeing that O'Toole was killed after being mistaken for her (Bond had Felix transport the dead body from the hotel to the apartment to convince Tiffany of the same), Tiffany changes her mind and decides to tell Bond about the next link in the chain. She drives Bond to the airport, where the diamonds are retrieved from a locker by a porter & given to Professor Metz (Joseph Furst), a laser refraction specialist, who is followed to a remote facility. Bond enters the apparent destination of the diamonds (by hiding inside Metz's van); a research laboratory owned by Whyte, where a satellite is being built by Metz. When Bond's cover is blown, he escapes by stealing a moon buggy (which was being used to train astronauts) and reunites with Tiffany. That night, they elude police officers who had been sent after Bond for the commotion caused at the laboratory.

Bond scales the walls to the Whyte House's top floor to confront Whyte. He is instead met by Blofeld who is alive along with his double, who use an electronic device to sound like Whyte (Whyte has not been seen for 5 yrs, so Blofeld found it convenient to conduct his activities under Whyte's name). Bond kills one of the Blofelds, which is revealed to be another a look-alike. He is then rendered unconscious by gas, collected by Wint and Kidd, and is taken out to Las Vegas Valley, where he is dumped in an oil pipeline and left to die. an automated cleaner is sent down the pipe to kill Bond..

Bond escapes, then telephones Blofeld, using a similar electronic device to pose as Whyte's assistant Saxby (Bruce Cabot). He finds out Whyte's exact location and rescues him after battling his female bodyguards, Bambi (Lola Larson) and Thumper (Trina Parks). Soon after, Saxby attempts to assassinate Whyte, but is killed. In the meantime, Blofeld abducts Case. With the help of Whyte, Bond raids the lab and uncovers Blofeld's plot to create a laser satellite using the diamonds, which by now has already been sent into orbit. Blofeld's team takes guidance control of the satellite and Whyte's men can no longer control it. With the satellite, Blofeld destroys nuclear weapons in China, the Soviet Union and the United States, then proposes an international auction for global nuclear supremacy.

Whyte identifies an oil platform off the coast of Baja California as Blofeld's likely base of operations (since Whyte himself had no installations there, so presumably Blofeld built it). After Bond's attempt to change the cassette containing the satellite control codes fails due to a mistake by Tiffany (who hands Bond the replacement tape. Bond switches the replacement tape for the real one and gives Tiffany the real one. She thinks Bond wants her to switch the tapes and she puts the real one back in), a helicopter attack on the oil rig is launched by Whyte, Leiter and the CIA.

Blofeld attempts to escape in a midget submarine, but Bond gains control of the submarine's launch crane and crashes the sub into the control room, causing both the satellite control and the base to be destroyed. Bond and Tiffany then head for Britain on a cruise ship, where Wint and Kidd pose as room-service stewards and attempt to kill them with a hidden bomb, but Bond discovers their plan and kills the two henchmen instead. As they embrace afterwards, Tiffany asks Bond, "How the hell do we get those diamonds down again?"