The plot, as seen through the eyes of a secret agent from the Moonlight organization, transports the reader to a relatively distant future where life on Earth is heading toward an inevitable catastrophe. The only hope for a dying civilization is to colonize distant planets in the Solar System and live on orbital stations orbiting Earth. But there's something more: a mysterious signal emanating from underground tunnels carved beneath the surface of the Silver Moon. This signal had been pulsating there for many thousands of years, but it was never meant to be discovered by the human race... it calls those who left our planetary system thousands of years ago to return from the deepest abysses of space.