The British Secret Service agent James Bond is sent on an assignment by his superior, M. Acting on information received from Special Branch, M tasks Bond with infiltrating a smuggling ring transporting diamonds from mines in the Crown colony of Sierra Leone to the United States. Bond must infiltrate the smugglers' pipeline to uncover those responsible. Using the identity of "Peter Franks", a country house burglar turned diamond smuggler, he meets Tiffany Case, an attractive gang member who has developed an antipathy towards men after being gang-raped as a teenager.
Bond discovers that the ring is operated by the Spangled Mob, a ruthless American gang run by the brothers Jack and Seraffimo Spang. He follows the trail from London to New York. To earn his fee for carrying the diamonds he is instructed by a gang member, Shady Tree, to bet on a rigged horse race in nearby Saratoga. There Bond meets Felix Leiter, a former CIA agent working at Pinkertons as a private detective investigating crooked horse racing. Leiter bribes the jockey to ensure the failure of the plot to rig the race, and asks Bond to make the pay-off. When he goes to make the payment, he witnesses two homosexual thugs, Wint and Kidd, attack the jockey.
Bond calls Tree to enquire further about the payment of his fee and is told to go to the Tiara Hotel in Las Vegas. The Tiara is owned by Seraffimo Spang and operates as the headquarters of the Spangled Mob. Spang also owns an old Western ghost town, named Spectreville, restored to be his own private holiday retreat. At the hotel Bond finally receives payment through a rigged blackjack game where the dealer is Tiffany. After winning the money he is owed he disobeys his orders from Tree by continuing to gamble in the casino and wins heavily. Spang suspects that Bond may be a 'plant' and has him captured and tortured at Spectreville. With Tiffany's help he escapes from Spectreville aboard a railway push-car with Seraffimo Spang in pursuit aboard an old Western train. Bond changes the points and re-routes the train onto a dead-end, and shoots Spang before the resulting crash. Assisted by Leiter, Bond and Tiffany go via California to New York, where they board theRMS Queen Elizabeth
to travel to London, a relationship developing between them as they go. Wint and Kidd observe their embarkation and follow them on board. They kidnap Tiffany, planning to kill her and throw her overboard. Bond rescues her and kills both gangsters; he makes it look like a murder-suicide.
Tiffany subsequently informs Bond of the details of the pipeline. The story begins in Africa where a dentist bribes miners to smuggle diamonds in their mouths; he extracts the gems during routine appointments. From there, the dentist takes the diamonds to a rendezvous with a German helicopter pilot. Eventually the diamonds go to Paris and then on to London. There, after telephone instructions from a contact known as ABC, Tiffany meets a person who explains how the diamonds will be smuggled to New York City. After returning to London—where Tiffany moves into Bond's flat—Bond flies to Freetown in Sierra Leone, and then to the next diamond rendezvous. With the collapse of the rest of the pipeline, Jack Spang (who turns out to be ABC) shuts down his diamond-smuggling pipeline by killing its participants. Spang himself is killed when Bond shoots down his helicopter.