In retrospect, the execution had been a mistake. Subsequently, the informant in Glabrio’s household had reported that at a dinner party, during the serious drinking after the food, thinking himself secure in his own home, safe among his own kind, the senator had made treasonous criticisms of the Emperor. Glabrio had mocked Gallienus Augustus as an effeminate and a coward and a fool. No wonder the empire tottered when the throne was occupied by a spendthrift who squandered money needed for the army on lavish buildings to flatter his vanity: a luxurious portico along the Flaminian Way; a statue larger than the Colossus on the Esquiline; Platonopolis, a whole city of philosophers in the Apennines. Was there no end to his profligacy? By all the gods, the majesty of Rome was dragged through the dirt by a degenerate who drank himself into insensibility, dressed as a woman, and was a slave to his lust for a barbarian mistress. Know a ruler by his companions. Gallienus surrounded himself with pimps and prostitutes, Greek philosophers and Syrian dancers. Reviling the Senate, the nobility of Rome, Gallienus gave high office and military commands to common soldiers, men who had started life as peasants or goatherds.

These might have been nothing but inebriated words, and no actual threats had been uttered, but then Acilius Glabrio changed the routine of a lifetime. This summer he had not retired to his villa on the Bay of Naples, but had remained in the swelter of Rome. A man who previously had paid no more than lip service to the demands of traditional religion, now, under the scorching August sun, had taken to traversing the city to attend obscure festivals in out-of-the-way shrines. Either the senator was seeking divine approval for some desperate act, or the ceremonies were a cover for clandestine meetings. Murena had decided it was time he saw for himself.

‘Vulcan, God of Fire, hear our prayers.’ The sacrifice was about to begin.

The priest held a fish caught in the Tiber. It twisted and gasped in his hands.

‘Mulciber, Quietus . . .’ The titles of the deity were intoned.

The priest threw the fish alive into the fire. Its silver scales hissed and blackened.

Murena continued to watch Acilius Glabrio, but his thoughts roamed. It was a skill he had learnt early as a frumentarius. Nothing must be missed, but if you gave all your attention to the object of your surveillance you drew attention to yourself.

The priest took another fish.

The strange sacrifice made sense to Murena. By offering things usually safe from Vulcan, it might induce the god of conflagrations to spare things that would burn only too easily in the hot season. Rome was largely built of wood, and the fear of fire was a terrible reality.

The next fish was added to the flames. The stench of the river was overlaid with an agreeable kitchen-like smell.