In July 1898, the combined Martian resistance, under lead of Warlord John Carter, was able to repel the invading alien molluscs, who then fled the planet and sought to invade Earth. When the first alien cylinder crashed in the English countryside, the league was called upon to investigate...

The strange foreign cylinder turned out to be much more foreign than expected. The league barely maked it out alive, when the alien molluscs turned their deadly heat ray on the crows of onlookers. The army was called in, and the league meanwhile retired to a nearby inn to rest and prepare themselves. When yet another cylinder is sighted streaking towards Earth, Mr. Griffin decided to take steps that would be of mutual benefit to himself and the invaders.

The army's advance on the invaders' crater having been disastrously unsuccessful, the league were rushed back to their British Museum headquarters to confer with Mycroft Holmes. Quatermain, Nemo and Hyde went on reconnaissance to the town of Maybury, where they encountered a terrifying mollusc tripod. Meanwhile, back at the museum Griffin brutally attacked Miss Murray, stealing London's secret military defence plans. In light of Griffin's treachery, Holmes decided to spreak the league out; Quatermain and Miss Murray are to find a doctor in the English countryside, while Nemo and Hyde are left to defend London against the tripods.

While Nemo managed to keep the invaders south of the Thames, Quatermain and Murray found the doctor they were looking for; Dr. Alphonse Moreau supplied them with the mysterious H-142 hybrid. Meanwhile, the Thames was filled with ghastly weed by the invaders, leaving the Nautilus disabled, and Hyde went to the museum to find Griffin, and then brutally slaughtered him. As soon as Quatermain and Murray arrive back in London, the H-142 was taken to Westminster, and the league assembled at London Bridge, where the tripods were amassed. In order to delay their advance, Hyde sacrificed himself, leaving the bridge blocked for the alien tripods. Soon after, the H-142, a hybrid of anthrax and streptococcus, was launched from Westminster, to exterminate the tripods in South London, and the people left there. Nemo, out of disgust for the British using a disease weapon, leaves the league, leaving only Quatermain and Miss Murray remaining...