In this second book, David and Larissa are at summer school. “Think of yourselves as the disciples of Carl von Linné," the teacher says encouragingly as he sends them out on an assignment, “but don’t go anywhere near the disused mine, whatever you do!" But that’s exactly what David and Larissa do. And as if that weren’t enough, they clamber down into the mine as well - chasing a mysterious man who’s kept turning up wherever they happen to be recently, and who has now disappeared down one of the shafts. The deeper into the mine they penetrate, the more remarkable things they stumble upon. Is there a connection with recent newspaper articles about the desecration of famous scientists’ graves? When Larissa ends up face to face with an exact copy of herself, they begin to suspect who it is they’re dealing with. It isn’t only David and Larissa who are under threat - the whole of mankind could be in danger!