I followed the line of the Cloaca Maxima, the Great Sewer, built five hundred years ago to drain the marshes round the Forum and the river side of the Aventine. My road soon brought me among the spice markets, where I came upon a watchman guarding the manhole where sewermen still plugged away daily under Nap Lane. They were not here today. On a public holiday no one works; only watchmen sometimes watch, if they want somewhere quiet to get drunk. This watchman had guzzled his way through one raw skinful and was taking a nap to encourage him for more.

So far nothing unexpected. Yet at the head of the alley I spotted a girl I vaguely thought I knew.

“Naïssa?” It was Helena Justina’s constantly abandoned maid.

She had made up her face with borrowed paint in honour of the day. She had done it in poor light so in broad sunshine the final effect passed beyond enhancing her features to a vivid glaze of colour; it gave her an unnatural, astonished stare.

“Where is your lady, girl?” I demanded anxiously.

“In her father-in-law’s warehouse. I was frightened to go any further; she told me to wait here.”

“It’s just a warehouse, nothing sinister; you ought to have gone in with her!”

“What shall I do now?” Naïssa queried nervously, widening her fantastically painted eyes.

“Whatever she told you, Naïssa!” I instructed unsympathetically, while my mind raced.

Having informed Helena Justina yesterday that I was not free to go to the warehouse, I knew I ought to abandon my present plan. I wanted very badly to see her, but turned away. Now I had accepted that at least one of her close relations was involved in the conspiracy, facing her was hard to contemplate. Yet all the time I kept remembering that the warehouse was where Sosia had been murdered. To leave Helena alone there would have been even more difficult.

“Are you Didius Falco?” Naïssa asked, with a glimmer of recognition in her eyes. I stopped. “She told me to go to your house with this—”

She was holding something out. It was wrapped in a scarf, but the weight felt familiar as soon as it dropped into my hand.

“Was there a message?”

“No, sir.”

Already I realized something serious was happening. I said urgently to the maid: “Go back and watch the Triumph with the family again. Tell Helena Justina’s mother, as discreetly as you can, that your lady is under my escort now. Her father should be attending the sacrifice, no need to bother him yet. But if Helena does not reappear by the time of the celebration dinner, go immediately to the senator and tell him where we are.”

The next time I began to walk it was rapidly down Nap Lane. As I went, I unfolded Helena’s scarf.