Professor Salvatierra, a professor at the University of Madrid, receives a strange letter from his friend Professor Reimann, director of a prestigious research institute in Duseldorf, in which he asks him to visit him since there are some internal plots and schemes going on at the Institute, and he needs Salvatierra's help. Salvatierra and his partner Cristina, a former student of his, take advantage of the summer to travel to Duseldorf and, shortly afterwards, Reimann disappears without a trace. Police link the disappearance to the murder of a small Turkish drug dealer. Salvatierra and Cristina, between the distrust of the German police and the harassment of a gang of criminals, are discovering the surprising reasons for the disappearance of the professor, in which intrigues in the academic world are intermingled with sinister activities of the Turkish Mafia in Germany.