The book is the sequel of the famous "The Lost World" by Arthur Conan Doyle. The work of Doyle is closed with two of the protagonists (Malone and Roxton) while they start to organize the return to the highland.
Edward D. Malone is the journalist of the Daily Gazette that he is admitted to the group of explorers to the conquest of the lost pinnacle in the middle of the tropical forest. Malone has to compile an account for his newspaper. The book is structured as a story narrated by Malone, which, after years, recalls that time and he turns to a hypothetical reader because, while he is writing, he doesn't know yet if his notes will ever take the form of book.
To the group of adventurers, that returns in the pinnacle in the middle of the forest, an eccentric entomologist it is added, doctor Stapleton.
In reality the finalities of the entomologist are mysterious and the true motive for his share will be known only at the end of the story.
On the lost pinnacle there is also a layer of diamonds that will also attract scoundrels and people without scruples. This will constitute a danger more in an Earth where the evolution seems gone crazy. Our heroes, once more, they will be in front to dinosaurs, raiders carnivores and starving birds.
Besides, a race of men-monkey that still lives on the highland, and that in the first trip had been defeated, now has taken upper hand on the local tribe of natives and must be defeats again.
But the greatest threat will be represented by a community of giant mantis, enormous carnivorous insects that have developed a social nature as ants or termites.
After an awful explosion, the pinnacle collapse on himself and the magma that is concealed in the viscus of the earth climbs in surface. The lost world dies and sinks together with its inhabitants. This time is lost indeed forever. Maple White, an eccentric and introvert American artist, is sheltered for years in a shelter built on the trees developing one particular philosophy and vision of the life. From the tall trees, in fact, it observes all the underlying things, understood the starving beasts that populate the highland.
He will prefer to stay in this world in flames and to die, rather than to make return to a civilization that doesn't feel to belong him anymore.
At the end it will be understood that the entomologist Doctor Stapleton had realized the presence on the pinnacle of these giant insects and he was united to the group of explorers to study them.
Doctor Stapleton will succeed in bringing out of the lost world the eggs of these mantis. He will do this without warning anybody of the other participants. Returned to the civil world, he will be withdrawn in an isolated place and it will start to study the insects.
For the last part the story occupies itself with the secret diary of Peter Stapleton, retired in Cornwall. The shocking fact revealed is the beheading of an eight years old boy in a quiet Cornwall town.
The book ends but the history shows an ample border for a sequel.