The expedition into the heart of the Great Void is launched, and Valerian and Laureline are on it. But in no time they're already facing the mysterious force that threatens the entire galaxy: the Wolochs, gigantic sentient monoliths dead set on destroying any civilisation that might stand in the way of their domination. Our two Human agents can't hope to stop the Order of the Stones by themselves, but fortunately, they still have allies...