He gazed at the bits of metal again. What they represented, Rhyme reflected, was obvious. A simple rearrangement resulted in yet another number. The ordinal ‘17th’.

Sachs had donned a face mask and double gloves. She was examining one metal character. The number 7. ‘We’ve got tool marks. Distinctive filing. That’s something.’

It might be possible to link the poisoned implants to a metal file in the suspect’s possession – provided that they found the file, of course; there was no national registry of tool marks, as there was for fingerprints, DNA and rifle slugs.

‘Source of the poison?’ Rhyme inquired.

Sachs went online and reported, ‘Well, this’s interesting. You know e-cigarettes?’

‘No.’

‘Smokeless cigarettes. They have batteries and a flavor capsule. There’s sort of a vapor you inhale. You can buy commercial nicotine, unflavored and in flavors, to add to the capsules. It’s in liquid form. They call it “juice”.’

What people do to their bodies, Rhyme reflected. ‘How many sources?’

‘Several dozen.’ Mel Cooper looked over the computer. ‘What’s for sale on the market is toxic, yeah, but nothing like this. The unsub either distilled that or made his own.’

‘Okay. What else do we have?’

Sachs had explained that wading through the ground floor of the parking garage and the tunnel had yielded nothing; the flood had been massive. Still, they had found some evidence on and inside the bag containing the implants.

The bag was a typical (and untraceable) food storage bag. At the top was a strip of matte-finish plastic so a cook could write down what the bag contained or the date it went into the freezer. Though the water had washed away much of the unsub’s writing, faint pink lettering remained. The message was No. 3 – for the third attack, Rhyme assumed.

‘Don’t know how helpful that is,’ Rhyme grumbled. ‘But put it on the board.’

Cooper ran several other samples. ‘Here’s a combination of human albumin and sodium chloride – the percentages are consistent with drugs used in plastic surgery procedures.’

‘Ah, that again,’ Rhyme said. ‘Our perp’s got in mind changing appearance. But can’t see him going under the knife quite yet. He’s too busy. But afterward, that’s part of his plan.’

Lon Sellitto called in. He had remained at the Belvedere to run the canvassing for witnesses. ‘Linc, nobody saw anything. You know what’s happening, don’t you?’

‘Enlighten me.’

‘People know this guy is using the underground to get close to his victims. They’re afraid that if they say they saw anything, he’ll get them in their bathroom or laundry room or garage.’