Three years after the events that took place in The Lost World, Professor Challenger urgently summons his fellow to a meeting. Oddly, he requires each to bring an oxygen cylinder with him. What he soon informs them is that from astronomical data and just received telegraphs of strange accidents on the other side of the world, he has deduced that the Earth is starting to move through a region of space containing something poisonous to humankind.
"And the folk in the coal-mines," said Summerlee with a dismal chuckle. "If ever geologists should by any chance live upon earth again they will have some strange theories of the existence of man in carboniferous strata."