It is the late summer of 314 and Rome is shocked by a series of violent abductions. Young men and women, sons and daughters of the powerful, are being kidnapped and held for ransom before being released in a rambling, haunted cemetery. At the same time, veteran soldiers, men who served Constantine along the Great Wall in northern Britain are being barbarously murdered. The indignities inflicted on their corpses recall the barbaric practices of the Picts against whom they fought so many years ago.

Claudia, "agente in rebus politicis" – or spy – is summoned by the Empress Helena to investigate and resolve these macabre occurrences. Meanwhile, Claudia has problems of her own. The corpse of a young woman, beautifully preserved and apparently buried some years previously, is accidentally disinterred in her uncle Polybius's garden. Who is she? How did she get there? Why is the corpse so carefully preserved? Claudia is faced with this wall of mystery. She must track her way through a murky tangle of politics, religion, greed and long-forgotten evil and is drawn into a game where the slightest mistake could cost her life.