The Ranger, a British nuclear submarine carrying 16 Polaris missiles, goes missing at the same time as its Soviet counterpart, the Potemkin. The Russians assign their best agent, Major Anya Amasova, to investigate the disappearance while the British send James Bond 007 on an identical mission. On his way back to London, Bond is ambushed while skiing in Austria and only survives by killing one of his enemies, KGB Agent Barsov. Anya, Barsov's lover, vows to avenge his death.
The disappearance of the submarine is particularly serious as it indicates that a submarine tracking system has been developed which could fatally undermine Britain's nuclear deterrent. The plans for this system have been stolen and are being offered to the highest bidder from a source in Egypt. Bond travels to Cairo to meet the source of the plans but before he can investigate any further, his contact Fekkesh, an intermediary of club owner Max Kalba, is killed by a mysterious assassin with steel teeth. This hired killer, Jaws, has been sent by the owner of the tracking system, millionaire Karl Stromberg, to recover the stolen plans and kill anyone who comes into contact with them. Stromberg, who lives in a huge underwater complex, intends to use the tracking system as the first stage in a plan to conquer the world.
At the Pyramids, Bond meets Anya and discovers that they share the same goal. They both go to meet Kalba but he is killed by Jaws before he can hand over the microfilmed plans. Bond and Anya hide in the back of Jaws' van and recover the microfilm after a fight in a deserted building site. The two agents squabble over possession of the microfilm but return it to Cairo where they meet their respective superiors; M, head of MI6, and General Gogol, head of the KGB. Britain and the Soviet Union have agreed to cooperate to recover the submarines. Examining the microfilm, it is discovered that vital technical information has been removed but a small mark indicates the source of the microfilm; Karl Stromberg's marine laboratory in Sardinia.
While travelling by train to Sardinia, Bond and Anya are attacked by Jaws who is defeated when Bond electrocutes his teeth with a table lamp. They are met in Sardinia by Q, who delivers to Bond his new car, a white Lotus Esprit. At the laboratory, Bond impersonates James Sterling, a piscatologist, and meets Stromberg, who tests him and is apparently satisfied. However, after their meeting Stromberg discovers Bond's true identity and orders his assassination. His female assassin, Naomi, is sent to kill the agents in a helicopter but is foiled when Bond demonstrates the aquatic abilities of the Lotus and destroys his pursuer with a sea-to-air missile.
Back at their hotel, Anya discovers that Bond was the killer of her lover, but declares that she will exact her revenge only when the mission is over. Meanwhile, the two agents are taken aboard an American submarine which is tracking the Liparus, a large tanker owned by Stromberg. Before a boarding party can be transferred, the bow of the Liparus opens up and 'swallows' the submarine. The Liparus is a holding dock for the stolen submarines, which are then relieved of their nuclear missiles. The crew of the submarine is taken into custody, but Bond and Anya are personally met by Stromberg.
Stromberg reveals his plans to launch missiles on New York and Moscow, thus precipitating a devastating nuclear war which will allow him to create a new underwater world without the interference of the rest of mankind. Before he can be locked up, Bond succeeds in evading his captors and encouraging the rest of the imprisoned sailors to revolt. The Liparus is destroyed and the nuclear missiles disarmed, but Stromberg escapes and returns to his underwater base with Anya.
Bond travels to the base, kills Stromberg and rescues Anya. Jaws attempts to kill him but is once more overcome, this time with a large electromagnet. Bond and Anya escape, minutes before the base explodes. Anya fails to complete her personal vendetta for she has now fallen in love with Bond.
