Towards the end of the nineteenth century, bizarre flashes of green light are witnessed coming from Mars. The unnamed narrator is assured by the astronomer Ogilvy, an acquaintance of his, that there is no possible chance of life on Mars — but the scientists of Victorian Britain are unaware that cold, inhuman intelligences have been greedily watching Earth from that world, and soon after a mysterious cylinder crashes to Earth in a field outside the town of Woking. The cylinder draws a crowd of curious onlookers, particularly after it begins to unscrew. Bizarre, tentacled lifeforms emerge from the craft but, having difficulty in Earth's gravity, soon withdraw. This prompts a group of experts, including Ogilvy and the Royal Astronomer Stent, to form a welcoming party to greet the Martians. When they approach the cylinder, however, a large funnel like object emerges and incinerates them with an invisible beam of energy, which they then turn on the panicking crowd.
The Narrator, lucky to escape with his life, flees the scene in terror and returns home. As the military begin to position themselves around the crater, daily life continues as if nothing is happening. Everyone confidently beings to believe that the Martians are weak and incapable of leaving their cylinder in the crater, but ominous sounds of battle can soon be heard. The Narrator decides to take his wife to safety in nearby Leatherhead, where his cousin lives, and rents a local publican's cart in order to do so. On his return from Leatherhead, however, the Narrator is horrified when he encounters a large tripod-machine quickly moving in the outskirts of town. The horse is killed, but the Narrator once again narrowly escapes, only to discover that Woking has been devastated by battle and many of his neighbours have been killed.
Sheltering in his house, the Narrator encounters a young artilleryman seeking shelter. The Artilleryman reveals that he is a survivor of a battle on the outskirts of the town between the military and the Martians, who have created large tripod fighting-machines to move around in; it was one of these that the Narrator encountered. The military have been routed by the Martians, their Heat Ray, and a chemical weapon that takes the form of black dust which kills anyone who inhales it. The Narrator learns that another cylinder has landed between Woking and Leatherhead, cutting him off from his wife. The Narrator and the Artilleryman join forces and attempt to escape, but are separated by a later Martian attack as they try to board a ferry at Shepperton. The Narrator escapes by boat down the Thames, where he encounters a local curate. The two are cut off from escape by the Martian invaders and forced to work together.
The narrative briefly transfers to an account of the Narrator's younger brother, a medical student based in London. Although the Martian invasion was initially ignored by those in the capital, the initial military resistance has been all but wiped out and more cylinders continue to arrive from space. As the Martians begin to attack the outskirts of London, the authorities order a sudden evacuation, and the Narrator's Brother is swept along with the panicked exodus to the east along with a pair of female friends. The Narrator's Brother sees firsthand how order and decency begin to break down in the panic, and protects his friends as they make their way to the sea. They manage to buy passage on a small steamer, but as the refugee boats flee a group of Martian fighting machines encounter them. The battleship HMS Thunderchild attacks the fighting-machine to buy the refugee ships time to escape, but while it manages to destroy one of them it is ultimately destroyed with the loss of all hands. Although the refugees, including the Narrator's Brother, manage to escape, all meaningful military resistance to the Martians has been destroyed.
The Narrator resumes the tale of his experiences. While ransacking houses for supplies, the Narrator and the Curate are trapped inside one when a cylinder lands on top of it. They remain trapped for two weeks, and this gives them an eyewitness view to the functions of a Martian base, and it soon becomes clear that the Martians have begun harvesting any survivors that they can find in order to drink their blood. The Curate, his nerves and beliefs increasingly strained during the invasion, begins to go completely insane on discovering this. After the Curate's rantings threaten to reveal their presence, the Narrator is forced to violently subdue the Curate but the sounds of their struggle attracts a nearby Martian. The Narrator manages to successfully hide, but the unconscious Curate is dragged away by the Martian to be drained of his blood.
Eventually, the Martians abandon their camp, allowing the Narrator to escape the ruined house. He discovers that during his imprisonment the world has been transformed, with the local vegetation becoming overrun by a thick red weed that is responsible for Mars's distinctive red colour. The Narrator begins to make his way to London, and on the way once again crosses paths with the Artilleryman. The Artilleryman, convinced that the Martians have overrun the surface of the planet, briefly convinces the Narrator of a grandiose scheme to rebuild human civilisation underground, but the Narrator soon realises that the Artilleryman is simply a lazy dreamer and abandons him.
Upon arriving at London, the Narrator discovers the city in ruins and abandoned. His experiences having taken their toll, the Narrator begins to lose his mind and decides to sacrifice himself when encountering a solitary fighting-machine; when the Martian doesn't kill him, the Narrator realises that the Martian inside is dead. This provokes a nervous breakdown which lasts several days, during which the Narrator is found and cared for by a local family of survivors. The family reveal that the Martians have all died, due to the various bacteria in the atmosphere that they lacked any kind of immunity or resistance towards. On fully recovering from his experiences, the Narrator makes his way back home to Woking, and learns that the town of Leatherhead was completely wiped out; by a miraculous stroke of fortune, however, his wife has survived, and the two are joyfully reunited. However, in concluding his tale, the Narrator admits that he remains unsettled by his experiences and the possibility of future attacks from Mars.
