Rhyme told him, ‘I need you to look for any pipes or reservoirs marked “hypochlorous acid”, “chlorine” or the letters “Cl”. They’d have a hazard diamond on them and probably a skin and eye irritant warning.’

‘Yes, sir. I’ll do that.’

The patrolman kept up a narrative as he walked from the place where the body’d been found, near the claustrophobia tunnel, to the bricked-off wall a hundred yards away.

Finally: ‘Nothing, sir. Only markings are DS and DEP stamped on the pipes.’ Department of Sanitation and Department of Environmental Protection, which was the agency overseeing the New York City water supply.

‘And some kind of boxes marked IFON – don’t know what that is. But nothing about chemicals.’

Sachs thanked him and disconnected.

Soon a member of the other team called in, from underneath the Provence2 crime scene – the slaughterhouse octagon, where Samantha Levine had died.

This officer reported the same. No DEP systems for introducing hypochlorous acid into the water system.

After disconnecting, Rhyme said, ‘So, it’s probably got some connection with the unsub. Let’s find out where somebody would buy it, or how it’s made. Ron?’

But a search revealed what Rhyme suspected: There were dozens of chemical supply companies in the tri-state area. And the unsub would have bought a small amount, so he’d use cash. He might even have stolen a can or two. A useless lead.

Rhyme wheeled forward to the examination table, staring at the implants, his mind considering the implications of the numbers.

1 7 t h

‘We have “the second”, “forty” and “seventeenth”. What the hell is he saying?’ Rhyme shook his head. ‘I still like the idea he’s sending us someplace. But where?’

Sachs said, ‘No scalloped border, like the others.’

But TT Gordon pointed out, ‘That was scarification, remember? If he was going to include them he would have used the same scalpel that he used to cut the incisions for the implants. He would’ve done that later, after he’d placed the implant. From what I heard, sounds like you interrupted him before he could get very far.’

‘Well, he escaped before he got very far,’ Sachs muttered.

Pulaski added, ‘No “the” with the seventeenth.’

‘Maybe that’s exactly how the quote goes, whatever that quote is.’

‘Implants take time, too,’ Gordon noted.

‘Good point. He’d want to move fast.’ Rhyme nodded toward the tattoo artist. ‘“The” might have been too much.’

Everyone’s eyes were on the numbers.

What the hell was the unsub’s message? What could he possibly be wanting to say to us, to the city, to the world?

If his model was the Bone Collector, as it seemed to be, that message was about revenge most likely. But for what? What did ‘the second’, ‘forty’, and now ‘17th’ say about a wrong he wanted vindicated?