James Bond is driving from Lake Garda to Siena, Italy, with the captured Mr. White in the boot of his car. After evading pursuers, Bond and M interrogate White regarding his organisation, Quantum. M's bodyguard, Mitchell, a double agent, attacks M, enabling White to escape. Bond chases Mitchell and kills him. Bond and M return to London and search Mitchell's flat, discovering through tagged banknotes that Mitchell had a contact in Haiti. Bond tracks the contact, Edmund Slate, and learns that Slate is a hitman sent to kill Camille Montes at the behest of her lover, environmentalist Dominic Greene. While observing her subsequent meeting with Greene, Bond learns that Greene is helping an exiled Bolivian General, Medrano—who murdered Camille's family—to overthrow his government in exchange for a seemingly barren piece of desert.
After rescuing Camille from Medrano, Bond follows Greene to a performance of Tosca in Bregenz, Austria. En route, the CIA head of the South American section, Gregg Beam, strikes a non-interference deal with Greene to maintain access to assumed stocks of Bolivian oil. Bond infiltrates Quantum's meeting at the opera, and a gunfight ensues. Greene's men kill a Special Branch bodyguard working for Quantum member Guy Haines, an adviser to the British Prime Minister, after he fights with Bond. M assumes that Bond killed him, and has his passports and credit cards revoked when he refuses to return home and debrief.
Bond convinces his old ally René Mathis to accompany him to Bolivia. At the La Paz airport, they are greeted by Strawberry Fields, an MI6 officer, who demands that Bond return to the UK immediately. Bond seduces her before they attend a party Greene holds that night. At the party, Bond again rescues Camille from Greene. Leaving, Bond and Camille are pulled over by Bolivian police working for Medrano. They had earlier attacked Mathis and put him in the boot of Bond's car to frame Bond; and, in the ensuing struggle, Mathis is killed. The following day, Bond and Camille survey Quantum's intended land acquisition by air; their plane is shot down after a brief air battle and they skydive out of the burning plane into a sinkhole. In the cave, Bond and Camille discover Quantum is damming Bolivia's supply of fresh water to create a monopoly. Back in La Paz, Bond meets M and learns that Quantum murdered Fields by drowning her in crude oil. M orders Bond arrested for disobeying orders but he escapes. He risks capture by doubling back to tell M that Fields demonstrated bravery in the field, and this is enough to convince M that Bond can be trusted.
Bond meets with CIA agent Felix Leiter, who discloses Greene and Medrano will meet in the Atacama Desert to finalise the coup. Warned by Leiter, he evades the CIA's Special Activities Division when they attempt to kill him. At an eco hotel in the desert, Greene reveals his true plans to Medrano: now that he controls the majority of Bolivia's water supply, Greene forces Medrano to accept a new contract that makes Greene Planet Bolivia's sole water utility company at significantly higher rates. Bond infiltrates the hotel, kills the Chief of Police for betraying Mathis, and confronts Greene. Meanwhile, Camille kills Medrano, avenging the murders of her parents and sister. The struggle leaves the hotel largely destroyed by fire. Bond then captures Greene and interrogates him about Quantum, before leaving him stranded in the desert with only a can of engine oil. Bond and Camille kiss before they part.
Bond travels to Kazan, Russia, where he finds Vesper Lynd's former lover, Yusef Kabira, a member of Quantum who seduces women with valuable connections. Bond tells Kabira's latest target, a Canadian Intelligence agent, of his true intentions, thus sparing her Vesper's fate. He spares Kabira's life and allows MI6 to arrest him. Outside, M tells Bond that Greene was found in the middle of the desert dead, shot twice and with engine oil in his stomach; Bond denies knowing anything. M also reveals that Leiter has been promoted and has taken Beam's place. She reinstates Bond as an agent; he tells M that he never left. As he leaves, he drops Vesper's necklace in the snow.