Every year, the poepchique boarding school where the three big bosom friends Emma, Rani and Zef celebrate a large Halloween party, with an auction of valuable objects. Top piece this year is an African red diamond. But a thunderstorm causes a power outage and puts the party room in the dark for a moment. When the lights come on again, the precious stone appears to have disappeared without a trace! Who stole it? And where did the thief hide the diamond? Questions that not only De Wolf, but also the world-famous investigator, Bill Clifford, and Emma, Rani and Zef set themselves …