‘That’s him. Billy broke into his shop, killed one of his associates. I think he wanted to kill TT but he was out. He might’ve found out about the tattoo artist some other way but that was the simplest explanation – seeing TT in my town house.

‘Since we learned that the motive for the group was domestic terrorism and that there was a tentative connection with you and your mother – the Bone Collector – I just wondered if it wasn’t too much of a coincidence that Seth had appeared in your life.

‘Of course, the unsub had the tattoo of the centipede. Seth didn’t seem to have any inkings; I’d seen him in a short-sleeve shirt. What to make of that? And then I remembered the waterproof ink – red ink – on one of the evidence bags. TT told us that some artists use washable pens like that to outline a tattoo first. Maybe that’s what he’d done – a temporary tattoo on his arm to trick us.’

Pam nodded. ‘Yes, exactly. He told me he’d draw it to make people think he was somebody else. Then wash it off when he was playing the role of Seth. It was a homeless man he tattooed with the centipede and paid to drill the hole. He was the one who died in the tunnel. He said he didn’t trust you to turn off the water pressure. He wanted to be cautious.’

‘Ah, so that’s who it was.’ Rhyme continued, ‘Then he broke into my town house and tried to poison me. We thought he was an expert with lock picks; there was no sign of jimmying the lock. But of course—’

‘He took the key to your town house off my keychain,’ Pam said, grimacing. ‘Had a copy made.’

‘That’s what I was thinking, yes. Was he the unsub? I couldn’t say for sure, of course, but I wasn’t going to take any chances. I called Dispatch and had some patrolmen get over here right away.’

Sachs said, ‘And the attack here yesterday. He faked it.’

‘Injected himself with a bit of propofol, then cuffed himself. He dropped the bottle of poison and the syringe on the floor and lay down to take a nap until the police showed up.’

‘Why?’ Pam asked.

Sachs added, ‘Wanted to keep suspicion off him. What better way than becoming a victim himself?’

Rhyme said, ‘And, I have to admit, our profilers contributed. Did some research that said centipedes in art and fiction represent an invasion of a safe, comfortable space. They lie in wait, invisible. That was Seth. Well, Billy.’

‘Sure was.’ Pam’s still eyes swiveled back to her apartment. She frowned, pulled a tissue from her pocket and licked it. She scrubbed away a smear of blood on her cheek.