The White Mountains and its sequels are set in the future, some one hundred years after aliens have invaded the earth. The great cities of the ancients lie in ruins, closed off to humans by command of the "Masters." Outside the cities people live a quiet rural life; the scientific knowledge that once permeated human society has been completely lost.

As the young protagonists travel across Europe to join a resistance group in the Alps, they come across many puzzling remains of ancient life, including a railroad. In one intriguing sequence they explore the city of Paris, entering the Metro, collecting supplies in a department store, and seeing traditional tourist sights such as the Cathedral of Notre Dame.