Dog-Headed Death. Ray Faraday Nelson

Meet Centurion Gaius Hesperian; a reflective and compassionate member of Emperor Nero’s palace guard with a knack for detective work. (He’s considered rather odd by his fellow officers because he doesn’t torture witnesses.) When Odysseus Memnon, a Greek-Egyptian shipping magnate, is found murdered in his Alexandrian mansion after annoucing his conversion to an evangelistic cult to which he plans to donate all of his worldly goods, it's up to Gaius Hesperian to solve the crime.