A quaestor is brutally murdered in Roman-occupied Colonia. A suspect is soon found – after all, the dagger in the body of the unpopular tax collector belongs to the freed slave Walraban. The young Teuton Rainolf is the only one who refuses to believe that his friend is the murderer; shortly before his arrest, Walraban managed to tell him that his weapon was stolen, presumably by two Tencteri. With the help of the Roman proconsul’s attractive daughter, Rainolf follows the trail of the two barbarians – never suspecting that he is endangering not only himself, but his family.
When, despite all the obstacles, he finally manages to corner one of the Tencteri, the man is dying. His last words are: "Caligula’s revenge will destroy you." What is that supposed to mean? How did the uneducated warrior know Caligula’s name, anyway – the name of the cruel Roman emperor who has been dead for decades?