Claudius took a deep breath and steadied himself. “In the days of Augustus, we wondered who might p-p-poison the emperor. Now we wonder whom the emperor might p-poison! And in both cases, the culprit is the same.”

Lucius looked up and down the street. There were few people in sight, and no one close enough to overhear them. Still, Lucius lowered his voice. “You mustn’t say such a thing, Claudius.”

“At least my nephew is well, as far as we know. P-p-poor little Caligula, an orphan! Surely no one would p-poison a seven-year-old boy.”

“Surely not,” agreed Lucius, thinking of his own sons, who were barely a year old. He reached up to touch the vacant spot at his breast; on this day he was not wearing the fascinum. He felt an urge to hurry home. “Come with me, Claudius. Acilia will want to hear the news. My mother will cook us dinner. You can spend the night with us.”

“No, no, no. I have too much to do. P-p-people to tell. Arrangements to m-make.”

“Then I’ll come with you,” said Lucius, trying to hide his reluctance.

“No, no, Lucius, you belong with your family. Go to them now. I shall be quite all right. No one would ever want to p-poison or put a spell on p-p-poor Claudius.” He turned away and hurried down the street.

Lucius looked after him until he disappeared around a corner, then headed home.

Even before he entered the house, he knew something was wrong. The door stood wide open. Where was the slave who minded the entrance? From within he heard the twins, Titus and Kaeso, crying loudly. Then he heard more-disturbing sounds: a man barking orders, the stamp of booted feet, the sound of furniture being overturned, a shriek from Acilia.

Lucius rushed inside. In the vestibule, the wax effigies of his ancestors were askew in their niches, as if someone had been rifling among them; the effigy of his father had fallen to the floor. He ran into the reception hall, from which he could see into the surrounding rooms. Soldiers had invaded his house and were busy ransacking it. From their imperial insignia he knew that they were Praetorians, the elite corps of centurions stationed in a fortified garrison just outside the city. The Praetorians were charged with guarding the emperor’s person and with apprehending the emperor’s enemies. What were they doing in his house, tearing the furniture apart, shaking out rugs, knocking holes in the walls?

“Stop this at once!” Lucius shouted.

The soldiers looked at him and paused. Two of them ran to him. While one held his shoulders, the other searched his person.

“No weapons!” the soldier shouted. They released him and carried on with what they were doing.

Acilia appeared, carrying Kaeso and Titus, one in each arm. The boys were red-faced and wailing. Their mother was ashen. She ran to Lucius’s side.

Following closely behind her was a tall man with a commanding presence. At his approach, the twins fell silent. Lucius recognized him: Sejanus, prefect of the Praetorians and right-hand man to Tiberius. The man’s steely gaze made Lucius’s blood run cold.

“What is the meaning of this?” said Lucius. “Why are these men looting my house?”

“Looting?” Sejanus smiled grimly. “Later, if an order of confiscation is issued, your possessions will be removed in an orderly fashion. But for now, Lucius Pinarius, my men are not here to rob you. They are here to search for evidence.”

“Evidence of what?”

“We shall know that when we find it.”

One of the soldiers approached. He held an unrolled scroll in his hands. “Prefect, I found this among the documents in that room over there.” He nodded towards Lucius’s study.

Sejanus took the scroll, blew dust off it, and studied it. His face grew long. “What have we here? By Hercules, I believe this is a horoscope that was cast for the emperor. What possible excuse can you give me for possessing such a document, Lucius Pinarius?”

Lucius opened his mouth but did not speak. Sejanus held the copy of a horoscope cast by Thrasyllus that Claudius had given him years ago as an example for him to study, when Lucius had tried and failed to master the science of astrology.

“No answer?” snapped Sejanus. “Where did you obtain this?”

Should he tell the man that the emperor’s own nephew had given it to him? Surely that would absolve him of whatever suspicion Sejanus harboured. Or would it? Claudius’s brother had just died, and Claudius clearly thought that Tiberius was responsible. Doddering, stuttering Claudius had always been considered outside the circle of those who might pose some threat to the emperor, but Claudius now had more motive than ever to hate his uncle. Telling Sejanus that Claudius had given him the horoscope might endanger Claudius. It might also endanger Lucius, making it look as if he were conspiring with his friend.

“I bought it from a vendor in the Subura, years ago, when I made a stab at learning astrology. I had no idea what it was. Look in my study, you’ll see a few works about astrology, and some other horoscopes as well, none of any importance. I haven’t looked at them in years. You saw yourself that this one was covered with dust.”

Sejanus glared at him. “I didn’t become prefect of the Praetorians without learning to tell when a man is lying to me. No matter. A new imperial order decrees that all practising astrologers, except those expressly retained by the emperor himself, are to be exiled from Italy. I would say that this document and the others you admit to possessing are ample evidence that you are among the class of persons to be banished.”

“But that’s ridiculous! I just told you, I haven’t even looked at those documents in years.”

“And if I examine these materials closely, will I find astrological calculations and horoscopes executed in your own handwriting?”

Lucius’s face became hot. “Perhaps. Years ago, I cast a few horoscopes, simply as exercises. But I am not and have never been an astrologer. I am an augur, as you can see by what I’m wearing.” Lucius impotently waved his lituus in the air.

Sejanus stepped closer, looming over him and looking down his nose. He was so close that Lucius could feel the man’s breath on his forehead.

“What sort of fool are you, Lucius Pinarius? Can’t you see that I’m offering you a way out?”

“I don’t understand.”

“Most enemies of the emperor have no choice about the charges brought against them, but I am giving you a choice.”

“Why?”

“Because I’m a nice fellow,” said Sejanus sweetly. “Because I love babies.” He glanced at the twins, who stared back at him in wide-eyed silence. “Because one way is more work for me, and the other way is less, you fool! Now, here are your choices.

“First choice: a charge of unauthorized possession of the emperor’s horoscope – a treasonable offense. If I bring that charge against you, there will necessarily be a very extensive investigation, and no one can say where that might lead; think of your friends, Pinarius. And the penalty is not only death for you, but confiscation of your estate; think of your wife and sons.

“Second choice: a simple charge of practising astrology without the emperor’s knowledge. In that case, you will be exiled from Italy, your destination to be determined by me, and only those materials that relate to the practice of astrology will be confiscated from you.”

Lucius looked at Acilia. She gazed back at him, trembling and terrified. Titus and Kaeso, sensing her distress, began to wail again.

“This is outrageous!” Lucius whispered. “My father was a senator. My grandfather was a nephew and heir to the Divine Julius, a cousin of the Divine Augustus-”

“While Tiberius was merely the stepson of Augustus? Is that what you’re saying? Are you questioning the legitimacy of the emperor’s claim to power? Are you asserting that you have a better claim?”

“No!”

“Is that why you possess a copy of the emperor’s horoscope? To discover on which days he is most vulnerable, so that you can plot his downfall and take his place?”