A missing explorer, mysterious stone formations, a sign in the sky - geologist Ella Jordan is faced with a mystery. As she ventures down to the lowest point on Earth, the events seem to make a terrible sense. From the Mariana Trench, signals come to the surface, that are far too regular to be of natural origin. In a submarine, Ella and scientist Konrad Martin dive to the bottom of the trench. The Challenger Depth appears to be the source of the disturbance. What they discover is a huge stone sphere, hard as diamond, that resists all common measuring methods. Suddenly, new signals occur: first from the North Cape region, then from Australia, then Antarctica. Ella and Konrad hurry around the world, encountering the same mysterious stone formations everywhere. All of a sudden the signals from the spheres begin to synchronize, their seismic waves generate earthquakes and volcanic eruptions all over the world - Ella is working obsessively on a solution, but the countdown is running ...