En 1914, dans les jours qui suivent l'attentat de Sarajevo, un officier autrichien essaye de sauver son ami, un officier serbe en mission en Autriche, alors que les menaces de guerre planent sur l'Europe.
Alors qu'on lui a demandé de travailler sur un projet ultra-secret, Joe Smith est enlevé. Il refuse de donner des informations malgré les coups et les menaces, et tient le coup en pensant à sa femme et à son fils. Il arrive à s'échapper et à conduire la police au repaire de ses ravisseurs, mais celui qui semblait en être le chef n'y est pas. Plus tard, il arrivera à le reconnaître grâce à sa bague et à le faire arrêter lui aussi.
Harry Palmer (Michael Caine), who has left MI5 to work as a private investigator, is told by a mechanical voice on the phone to take a package to Helsinki. The package contains six virus-laden eggs that have been stolen from the British government's research facility at Porton Down. In Helsinki, he is met by Anya (Françoise Dorléac) who takes him to meet her handler, Harry's old friend Leo Newbigen (Karl Malden). Leo is in love with Anya, but Harry knows that she is only pretending to reciprocate. Leo takes Harry to a secret room where a computer issues daily instructions to Leo and Anya. The computer speaks in the same voice as the one which summoned Harry to Helsinki.
In the spring of 1939 in England, Oxford University professor Richard Myles (Fred MacMurray) and his new bride Frances (Joan Crawford) decide to honeymoon on the continent. Because they are American tourists and therefore "above suspicion," they find themselves commissioned by the British secret service to find an apparently missing scientist who has developed a countermeasure against a new Nazi secret weapon, a magnetic sea mine. Without knowing his name, what he looks like, or where to find him, the couple look upon the search as adventurous and cross Europe seeking clues from clandestine contacts.
Issa Karpov (Grigoriy Dobrygin), a political refugee from Chechnya who has been tortured by Russian security forces, enters Hamburg, Germany, illegally.
A British couple, Perry (McGregor) and Gail (Harris), get embroiled with a Russian oligarch and high-profile money launderer Dima (Skarsgård) while on holiday in Marrakech. Dima leads them into a tortuous journey through Paris, the Swiss Alps and London.
The movie takes place as two parallel plots separated by couple years: In 1982, Wylie Cooper (Moore), is an engineer developing a targeting system on a tank for the United States Army. In 1984, Murphy is US Army Lt. Landry, an American tank commander sent to Kuwait to demonstrate "XM-10 Annihilator", America's latest main battle tank, which is equipped with Cooper's system. Because of the tank's poor design and shoddy construction, Landry and his crew are barely able to control or navigate the XM-10 before it leaves the proving grounds and wanders into a combat zone during Iraq's invasion of Kuwait (an unintentional foreshadowing of the Gulf War that occurred six years after the release of the film).
English tourist Iris Henderson (Margaret Lockwood) arrives at the "Gasthof Petrus" inn in the fictitious country of Bandrika, "one of Europe's few undiscovered corners". Iris is returning to Britain to marry a "blue-blooded cheque chaser", but an avalanche has blocked the railway line. The stranded passengers are forced to stay the night at the inn, including Charters and Caldicott, cricket enthusiasts who want to return to England to see the last days of the Test match.
In August 1939, a motley group of travellers find themselves in a small hotel in Bavaria, awaiting a delayed train to Switzerland. They include a "much married madcap American heiress", Amanda Metcalf-Midvani-Von Hoffsteader-Kelly, and Robert Condon, a wise-cracking American photographer.
In 1940, Linda Voss (Melanie Griffith), a young woman of Irish/German Jewish parentage, applies for a new job as a secretary with a New York law firm, but rejected as she didn't graduate from a prestigious women's college.
A Soviet spy (Perkins) is on an official mission to obtain sensitive information from NATO about military mobilization. The klutzy intelligence operative has to rely on the instinct of his new partner and love-interest Penelope Lightfeather (Bardot) as they traipse across the countryside, avoiding counter intelligence agents and distrustful communist operatives.
Three MI6 agents, including one "on loan" to the American government, are killed under mysterious circumstances within 24 hours of each other in the United Nations, New Orleans and a small Caribbean island, San Monique, respectively, while monitoring the operations of Dr. Kananga, the island's dictator. James Bond, agent 007, is sent to New York City to investigate the first murder. Kananga is also in New York, visiting the United Nations. Just after Bond arrives, his driver is shot dead by Whisper, one of Kananga's men, while taking Bond to meet Felix Leiter of the CIA. Bond is nearly killed in the ensuing car crash.
In an opening scene before the credits an assassin, Banat, is seen preparing a gun while a gramophone skips as it plays. The story that follows is the narrative of a letter from Howard Graham, an American armaments engineer, to his wife Stephanie. While journeying to the Soviet port of Batumi to return to the United States to complete his business with the Turkish Navy, Graham and his wife stop in Istanbul and are met by Kopeikin, a Turkish employee of Graham's company, who under the pretense of discussing business, takes Graham to a nightclub to introduce him to dancer Josette Maretl and her partner Gogo. When Banat tries to kill Graham during a magic act, he shoots the magician instead, and Graham is brought to the headquarters of the Turkish secret police for questioning. Colonel Haki of the secret police warns Graham that German agents are trying to kill him to delay the re-arming of Turkish ships. He shows Graham a photograph of Banat, whom he says was hired by a Nazi agent named Muller, and orders Graham to travel secretly to Batumi aboard a tramp steamer instead of by train. Haki assures him that he will personally see that Stephanie gets to their hotel in Batumi ahead of him.