Rome, 46 B.C.: Caesar arranges for the defeated Prince of the Celts to be paraded in triumph through the town - and with him, the legendary Celtic gold! It goes without saying that Cornelia and her friends Titus, Gaius and Publius are there in the midst of the crowd, enjoying the spectacle. In all the turmoil they learn that a gang of street kids are plotting to steal the gold of the Celts from the Temple of Saturn!
In order to thwart their plan, the quartet of amateur detectives devises an audacious strategy of their own: one of them will have to infiltrate the gang. But until such times as Cornelia and the leader of the gang, the highly mysterious »Gladiator's Son«, finally come face-to-face, the four friends have to work their way through a mass of fiendish riddles and dangerous ordeals which require all the courage they can muster - and the reader's greatest powers of deduction.