Barely have the detectives from o-vier solved their first case when Tivaro's grandfather unexpectedly ends up in the hospital and hands his grandson a few strange silver keys and an old chess set. Shortly thereafter, Tivaro discovers a more than seventy-year-old map of a tunnel that is said to lead to a million-dollar treasure hidden in the Taunus from the Nazi era. It won't be long before the four young detectives find themselves no longer alone in their search, as the greedy Professor Raff would go to any lengths, even over corpses, to enrich himself.

The author Merlin T. Salzburg wrote this crime novel at the age of twelve and has since been recognized as Hesse's youngest crime author. With his debut work 'Tivaro in Danger,' he began the exciting new youth crime series o-vier from the Frankfurt metropolitan area a year earlier. And as is to be expected in a good crime story, the four friends Tivaro, Otto, Nico, and Jojo quickly find themselves in the next hair-raising adventure. So, thrilling hours and delightful reading enjoyment are guaranteed.