A pattern of blood - Rosemary Rowe

Freedman and pavement-maker Libertus feels nothing but dismay when he is asked by his patron, Marcus Septimus, to accompany him to Corinium (modern Cirencester) to investigate a threat against a decurion, Quintus Ulpius. Meddling in murky political intrigue is a certain short-cut to an early grave, but Libertus cannot refuse his master, and he soon finds himself en route to Corinium as a personal guest of the decurion.

Libertus's feeling of unease turns to horror when he and Marcus arrive. They've only been at the villa for a matter of minutes when Quintus is found dead, stabbed in the back. Then one of his enemies is found with bloodstains on his toga, and for Marcus at least, the case is closed. But Libertus isn't as confident as his patron that the killer has been apprehended, and when a second body is found, he knows he must act fast before other lives, including his own, are threatened...