Lentullus was teaching my daughters to march up and down the hallway, bearing new little wooden swords. I recognised the wood (I had been saving it to make a pantry shelf, one day, in about ten years' time.) Lentullus, babysitting? Julia and Favonia dumped with a legionary? I knew what that meant too. Helena had not just taken Albia to make her look respectable, she had commandeered the new nursemaid, Galene, as well. And that meant, Helena Justina thought that if she saw Titus Caesar without me, she seriously needed chaperons.

Dear gods. And I had nearly let this feckless, faithless woman rub ointment on my sore toe.

'You'll never catch her now!' sneered Clemens. 'She's long gone, Falco. '

I declared it would be a gallant gesture to escort my lady home after her royal interview. It sounded feeble, and if I did set off for the Palace I knew my doubts would grow worse with every step I took. Titus Caesar was commander of the Praetorians, and thus in control of Anacrites. Helena was right. She stood a good chance of persuading Titus to free her brother – perhaps better than her father trying to work on Vespasian. The Emperor tended to leave his subordinates to operate as they chose; he would avoid countermanding Anacrites unless the Spy was very clearly in the wrong. Titus always boasted he enjoyed doing daily 'good deeds'; Helena would persuade him that generosity to Justinus was classic Roman virtue. Would a man of virtue (a species I distrusted) want classic repayment, however?

'Helena Justina seemed anxious, Marcus Didius. Something to do with a relative, is it?' I refused to respond to this blatant curiosity. When I demanded to know why Clemens was hanging around at home instead of out on the search for Veleda, he suggested I might need company. He didn't mean at the Palace; it seemed I was going somewhere much more unsavoury. 'Man came to see you last night, Falco. Petronius, would it be? Big stiff with a sneer on his face, said he was in the vigiles.'

Like me, and like all ex-soldiers, Petro believed the recent military intake was shoddy. Recruits were rubbish, officers were second-rate, discipline had deteriorated and now that Petronius and I were no longer defending the Empire, it was remarkable its entire political structure did not disintegrate.

I concede that in our day we had the Boudiccan Rebellion. On the other hand, once the legions got to grips with her, Queen Boudicca was eliminated without a trace. Unlike Veleda, she was not now scampering around Rome, gazing at the sacred monuments while she plotted acts of terror right at the foot of the Capitol and made us all look fools. 'You could have told me before! What's his message, Clemens?' 'Our woman has been spotted talking to vagrants.' 'Did he say who? Or where the sighting happened?' 'No, Falco – Oh, I think he mentioned it was on the streets at night. ' 'Very specific!' If! had known this, I would have got up and done something about it several hours ago. Even Helena had not seen fit to pass on this message. She knew about it though: 'Helena Justina,' said Clemens, citing her name with exaggerated respect, 'said be sure to take backup, if you go out interviewing rough people.' He was making me sound a wimp, in a way that Helena would never have done; she knew I could look after myself 'Helena told us you will go to find the runaways that your friend told you about, on the Via Appia.' This was Helena subtly reminding me what Petro had originally said. 'Daytime would be best, when they are all sleeping up among the tombs; you'll lose them when they come into the city scavenging at night.' I felt my mouth tighten. 'And she doesn't want you bringing any parasites or skin diseases home, so please go to a bath house afterwards. She's left your oil and strigil out.'

Now I wished I could have done this early enough to have then dropped in at Titus Caesar's boudoir when I stank of tramps and could give the imperial playboy lice. 'Anything else?' I asked Clemens in a nasty tone. 'I've ordered horses,' he responded meekly. I hate horses. If he did not know that already, he soon worked it out. I should have known any plan devised by an acting centurion would be a time-waster. Clemens had thought it was clever for us to leave Rome by the Ostia Gate, pick up the mounts he had arranged – which were not horses but donkeys; I could have told him that – then ride right around outside to the south of the city. It was a long way. It was the lazy way, too, and it took far longer than briskly walking across, which is what I would have done, left to myself Only my abstraction caused by Helena being with Titus let Clemens bamboozle me into this crazy scheme.

Clemens brought a soldier who had not crossed my path and annoyed me yet, Sentius. I had asked for my old comrade Lentullus; apparently he had to stay with the children, on Helena's orders. I thought twice about leaving my two precious ones with the clumsiest legionary Rome possessed, but Helena had a knack for choosing unexpected nursemaids. I ordered Lentullus to remove the wooden swords because I did not wish my tiny offspring to turn into frightful martial types who would be mocked by social poets: galumphing gym-frequenters, the shame of their parents, who would never acquire husbands. Lentullus just said, 'Well, they're happy and it's keeping them quiet, Falco.' I was only their father. Overruled, I left him to it.

Sentius was a tight-lipped, terse type, who viewed me with brooding suspicion. I thought he was trouble too. He was too big for a donkey and had staring eyes. He spent most of the morning eating an enormous almond pastry. Meanwhile Clemens kept digging into a bag of seeds and pine kernels, which he never offered round.

At least fretting about the wife, the children, the route, these companions, and the fact that I had had no breakfast stopped me losing my temper over the beast I was supposed to be riding. I had been given the truculent one with mange, who kept stopping dead. It was past noon when we reached the Appian Way necropolis. The houses of the dead stretch out from the city for several miles along the ancient highway. Packed tombs line the worn cobbled road to the south between stately groups of umbrella pines. Occasionally we saw funerals taking place. There would be more cremation parties after the festival, when Saturnalia indulgence and violence had taken its toll. People usually came out here at holiday time to feast with their dead ancestors, but chilly weather and dark nights must be putting them off Mostly the road was empty and the lines of rich men's mausoleums looked deserted.

As we slowed our mounts when we started to look for vagrants, we pulled our cloaks tighter across our chests, burying our ears in the fabric. We all became morose. It was a cold, grey day, a day for things to go badly wrong with no warning.

None of us had brought swords. I had not even thought about it, because weaponry was forbidden in the city. My automatic failure to carry had lacked forethought. Wandering between these isolated tombs in bad light was a dangerous idea. This was a situation where we were asking to get hurt. At first it seemed that Petronius must be wrong. We saw no sign of people living rough. We had all heard stories of successful beggars who were so good at their craft they became millionaires; beggars who treated importuning as a business and worked from secret offices; beggars who went home in a litter every evening, rid themselves of their rags and filth, and slept like kings under tapestry coverlets. Perhaps all beggars were like that. Perhaps Rome, where good citizens are generous benefactors, really had no homeless people. Perhaps in winter rich, kindly widows sent all the vagrants on holiday to airy seaside villas where their hair was trimmed, their sores were cured and they listened to improving poetry until they suddenly reformed and agreed to be trained as sculptors and lyre-players… Romancing, Falco.