The story is told retrospectively by an unnamed narrator, an educated, philosophically trained man who witnessed many of the events he describes and reports them as recent history. The first signs of an invasion from Mars come when astronomers note a series of spectacular explosions on the planet. Experts, however, think they were caused by meteorites or volcanic eruptions; no one suspects any danger. Only later does it become known that climatic changes steadily had made Mars less hospitable for its inhabitants, and they were looking to Earth as their only refuge. The explosions were the firing of ten projectiles, each containing a small Martian invasion force, at Earth.
The first cylinder-shaped projectile lands southwest of London, on a summer night. By morning, it has attracted a crowd of curious onlookers. In the early evening, the cylinder opens to reveal a grotesque, octopus-like figure the size of a bear, its body glistening like wet leather. The crowd retreats in shock. By dusk, an official deputation arrives, waving a white flag. The authorities have decided that the Martians are intelligent creatures and wish to communicate with them. A devastating beam of heat shoots out from the invaders’ cylinder, destroying everything it touches. Forty people lie dead, and the narrator flees in terror.
This sets the pattern for the next few days. The Martians appear to be unstoppable. They construct huge tripod-shaped machines, higher than a house, within which they sit, covered by a hood. The machines stride across the country, causing death and destruction wherever they go. Military might is useless against them: Troops and weapons are annihilated in large numbers. The narrator manages to escape the deadly heat ray by diving into a river. He meets a curate who believes that the day of judgment has come.
The narrative switches to London as the narrator tells of the experiences of his brother. News is slow to reach the capital city, but when it does, it is grave: The Martians are advancing on London and are releasing a poisonous black smoke that suffocates everything in its path. There is no defense against it. The entire population of London flees northward in a stampede of six million panic-stricken people. The Martians take possession of the city, although they also suffer losses: A warship rams and kills one Martian who has waded out to sea, and another Martian is killed when the same ship explodes after being struck by the heat ray.
The narrator hides with the curate in an empty house to escape the black smoke. Trapped for fifteen days by the presence of Martians outside, he observes them at work and learns to his horror that they feed on human blood. The curate loses his mind, and in a struggle, the narrator kills him. When he emerges from the house, he realizes that humanity’s rule over Earth has ended, and he encounters an artilleryman who has visionary ideas about what people must now do to survive.
The narrator makes his way to the deserted London, where he comes on a Martian emitting a strange crying sound. He then stumbles on the remains of a dead Martian; he soon finds fifty more. The Martians have died because they have no resistance to Earth’s bacteria. The joyful news is telegraphed across the world, and relief comes to the stricken city.