Young Natalie, a French au pair visiting a Hamburg family, is murdered. She is found dead with more than 8,000 euros in her pockets – hanging from a subway bridge. Since the woman apparently had no social contacts in Hamburg, the search for a potential perpetrator is extremely difficult. Her German au pair parents are also soon eliminated as suspects. Then the suicide note from Bechter brings the first investigative approach: he mentions a beautiful girl named Natalie and describes her in such detail that Holicek and Casstorff agree: the beauty must have been Natalie. Questioning people in Bechter 's environment lead the inspectors to Hamburg's gambling milieu.
But it soon becomes clear that the murder has nothing to do with the conventional legal and illegal gamblers and their establishments. Again, the commissioners seem to be stuck in a dead end. New evidence suggests that a completely different dimension of illegal gambling is captivating people in Hamburg. A so-called "cube room" is the constantly changing place where decisions are made not only about money, but also about fate and even life and death. In order to find the solution to the Natalie case, Casstorff has to play a dangerous game himself.