Rogue Emperor

It was a clear spring day, just a hundred years after the birth of Christ, when Jerry Pierce wandered into the Roman Colosseum to spend a quiet afternoon watching gladiators fight to the death. Sixty men had been killed already, not including the 15 condemned criminals executed at lunchtime, when an explosion rocked the arena. Bodies flew from the broad terrace just above the arena where the emperor had been presiding over the event. Shrapnel sliced through an enormous awning that shaded the seats, and a cloud of oily black smoke rose above the crowd. It was clear to Pierce--a traveler from the 21st century--that the explosion had probably been caused by an antitank missile.
Emperor Domitian was dead, and Pierce was ordered to investigate the assassination for the Agency of Intertemporal Development--an assignment that would pit him against the best of Rome's gladiators.