Just went on Audible, and I found this: "'Nine for the Devil: A John the Lord Chamberlain Mystery, Book 9.'" It's by Mary Reed. The blurb reads as follows:
"The year is 548, and Empress Theodora is dead of disease. Such is the belief of everyone in Constantinople, capital of the Roman Empire - everyone except Emperor Justinian, who orders John, his Lord Chamberlain, to find her murderer or suffer the consequences.
There is no sign of foul play, but many of the aristocrats at the imperial court had good reason to want Theodora dead. Suspects include General Artabanes, forced to occupy a house with an unloved wife, and Justinian’s cousin Germanus, who has seen his career blocked. Also suspect are Antonina and her husband, General Belisarius, enraged by Theodora’s attempt to marry their daughter to her grandson by compelling the young couple to live together. Could the exiled and much hated former tax collector John the Cappadocian have played a role? Might Gaius, palace physician, have tampered with Theodora’s medication? Pope Vigilius, who was detained in the capital due to a religious controversy, is not above suspicion. Even friends of John the Lord Chamberlain are acting strangely, including Anatolius the lawyer and Felix, captain of the palace guards.
As if it isn’t difficult enough to seek a murderer who seems to be a figment of the emperor’s grief-deranged imagination, John must also grapple with domestic upheavals. His daughter, living on an estate outside of the city, is about to give birth, and his aging servant, Peter, is dying. Will John be able to serve justice, his loved ones, and the emperor?"
Wow, the Eastern Empire. Neat!