Leafdown Crevice is totally unknown to any living creature except for the Intropodes who live there.
The Intropodes are small and white, hardly ever speak, and have bluish-green eyes and enormous hands and feet. They are very much creatures of habit and when possible prefer to remain inside the homes they have dug out at the bottom of the crevice or on its lower walls. There they devote themselves to composing elaborate mosaics, playing with balls made of mud and twigs, or exchanging extremely taciturn gossip. They don't much go in for curiosity, and for everything that happens they immediately find an irrefutably valid explanation.
In their favour, it must be admitted that they do have a kind of sense of humour.
As the years pass - extremely slowly - the Intropode population grows steadily. This makes it necessary to construct new dwellings higher up, ever closer to the Great Opening, the rip in their roof of darkness from which light and scents filter down from the world above.
The certainties of the Intropode mentality and society are shaken to the roots by this revolutionary development, and a fanatical movement develops among them denouncing the inhabitants of these new dwellings as enemies of the Intropode tradition and betrayers of its values.
The most extreme manifestation of this shocking but necessary advance towards the light is the new 'cluster homes'. For the moment, only one couple - by the name of Hsha and Hehz - has had the courage to actually go and live in one of these. Obviously, they are the cause of intense outrage and scandal among the more conservative Intropodes, but up there in their relatively illuminated gloom Hsha and Hehz don't attach much importance to the goings-on beneath them. On the contrary, they become increasingly fascinated by what is going on above them and are gradually drawn to explore new experiences and habits.
This alone would suffice to unleash the venom of their critics, but the last straw for them is the arrival on the scene of the couple's daughter, Huhz, who is born darker skinned, bigger and noisier than any previous Intropode.
The child's descent to the bottom of Leafdown Crevice for a holiday with her grandparents sparks a bitter revolt in the claustrophobic and conservative world of the Intropodes which soon brings their whole society to the brink of definitive implosion.
The prime cause of this threatened catastrophe becomes the last hope of avoiding it: everything depends on little Huhz.