In her firm, swift strokes, she outlined the networks.

Rhyme said, “Now add public works. Sewers. But just the older ones, from historical maps. Old shit, remember? And open, not enclosed, pipes. The Composer stepped in the trace.”

The young officer began a new search. The maps Ercole found were obviously incomplete but they showed some sewage sluices that had been in operation in the eighteenth and nineteenth centuries. Daniela put these on the map.

“Okay, now eliminate the walking-tour routes,” Rhyme instructed.

Ercole printed out the website information from “Underground Naples, See History Up Close!” and a half-dozen others. Daniela noted the routes and marked off any that coincided with the passageways and sewers they’d found.

Still, miles and miles of places to stash the victim remained.

Rossi said, “And an area where prostitutes worked, you were suggesting?” He looked at Giacomo, who gazed at the map and said, “I have patrolled—you would say in vice squad—many of the areas where working women and men are found, the Spanish Quarters, Piazza Garibaldi, Corso Umberto, Gianturco, Piazzale Tecchio—the San Paolo stadium, Via Terracina, Fuorigrotta, Agnano and Corso Lucci. These are active now. The Domiziana—or now Domitiana—area, north and west of Naples, was known historically for prostitution, and still is. But it’s very congested and the population is mostly immigrant. It would be hard for the Composer to get his victim there. And no underground passages are nearby.”

Rhyme said, “Circle the first areas you have mentioned, Officer.”

Giacomo took the marker from Daniela and did so.

This narrowed down the number of passageways and chambers to about two dozen.

“What are they exactly,” Sachs asked.

Rossi said, “Roman roads and alleyways and sidewalks before they were built over. Tunnels for delivery of merchandise to avoid the congested streets. Water reservoirs and aqueducts. Grain warehouses.”

“Water?”

“Yes. The Romans built the best water delivery infrastruttura in the world.”

Then Rhyme called, “Beatrice, you found limestone and lead?”

She didn’t understand, and Ercole translated.

“Sì. Yes, we did. There it is, you can see.”

“Were the old Roman aqueducts limestone?”

“Yes, they were and, as you are suggesting, I believe, the pipes…shifting the water, transporting the water to the fountains and the homes and the buildings, were lead. Now replaced, of course, for healthy reasons.”

“Ercole, maps of Roman water supplies?”

This document was readily available in the historical archives.

Ercole handed the printout to Daniela. He pointed to the document and said, “Here I have ten Roman water-holding chambers in the areas we have marked. They are like large wells or silos, round. These were connected to aqueducts coming into the city from the north and west. Some of them are large municipal reservoirs, twenty by twenty meters, and some are those serving smaller areas or individual homes, much smaller. When the supply of water became more modern, and pumping stations were created, many of these reservoirs were converted to warehouses and storerooms. Doors and windows were carved into the walls.”