In Dark Omens, Rosemary Rowe’s latest historical mystery set in Roman Britain, her pavement-maker/detective Longinus Flavius Libertus must solve a murder as the Empire reels from news of the death of Emperor Commodus.

How did the Libertus books come about?

It grew out of a short story I wrote for an anthology. The editor said nice things about the character, commenting that it would make proper series—so I tried, but it didn’t really gel at first, and I was never satisfied with my attempts until I hit on the idea of making it a first-person narrative (it was third-person in the original short story)—so Libertus can comment laconically on the Roman way of life without taking it for granted.

Why make your sleuth a pavement maker?

It was the idea of seeing patterns in the first instance but the role of mosaicist has advantages. It makes him a tradesman, which gives him an entree into that milieu and makes it possible for him to mix freely with artisans and shopkeepers, while allowing him entrance into the houses of the rich and conversations with wealthy would-be “customers.” Not many people could move between social strata in this time period, the idea of rank was a very rigid one and most tradesmen would never have crossed the threshold of a rich man’s house—any more than most rich men would have visited a shop while there were slaves to send. He has the advantage of a powerful patron too, which gives him borrowed clout and is the usual reason why he gets reluctantly involved. There weren’t really anything like policemen at the time—the aediles were only market police and the town watch was really only occupied with keeping violence off the streets and vagrants out of town.

What did making him a freed slave add?

This gives him entry into yet another class. Slaves open up to him, where they would not have dared to speak had they not known his history. It also enables him to understand their lives and have a degree of sympathy. He treats his own with a kindliness, which would not otherwise be very true to the period—all of which makes him a little more sympathetic to the readership, I hope.

What about Roman Britain most surprised you?

I think probably the similarities with people nowadays. I was ready for the differences, and the architecture and things, but discovering that chariot-racing fans wore colored scarves to meets, depending on which team they supported, and had to be separated from rival fans in case there were riots afterwards, and that the charioteers were traded between teams in the “off-season,” and were paid by local shop-keepers to be seen in the forum wearing so-and-so’s sandals and drinking someone’s wine—that was unexpected, and rather a delight.

What inspired the plot for Dark Omens?

Reading about how the slightest deviation from religious ritual was believed to be an ill-omen, together with the fall of Commodus, and reading of a body discovered in a frozen pond in the blizzard of the 1890s. I started to think about what life would have been like if there was a severe winter here in Roman times.