Rome. AD 71. Marcus Didius Falco, now Imperial Agent to Emperor Vespasian, is keeping busy tidying up corpses, kicking over the traces of a failed coup, making a bit on the side in stolen lead ingots. But a new plot to usurp the purple robes of power puts Falco on the back of a mule with a one-way ticket down the Appian Way - bumping into trouble, treason and Helena Justina, a senator's daughter he's trying hard to forget.