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.'
Rhyme couldn't argue with that attitude. What could be more frightening than to think you were alone and safe in the lower levels of your home or office or a public building and learn that you weren't alone at all; you had lethal company. Like a moist, venomous centipede uncurling under the blankets of your bed as you slept.
Sachs had brought Braden Alexander's clothing too. Cooper went through each item carefully but the water had eradicated all trace - if there'd been any in the first place, which was unlikely, Sachs said, because the contact between the two men had been minimal. The handcuffs revealed no trace and, like the others, were generic.
Cooper ran other samples of swabs from the implant bag. Most were negative. But finally he had a hit. Reading from the computer screen, he said, 'Hypochlorous acid.'
Rhyme looked over the mass spectrum. 'Curious. It's pure. Not diluted.'
'Right.' Cooper reached under the face shield and shoved his glasses higher on his nose. Rhyme wondered, as he often did, why he didn't get frames that fit.
Hypochlorous acid - a form of chlorine - was added to New York City drinking water, as in most cities, for purification. But because this sample was undiluted, it had not come from the flood that had destroyed the Belvedere parking garage crime scene. This was the form of the chemical in its pure state, before it was added to the water system.
Rhyme said, musing, 'It's a weak acid. At higher levels, I suppose, it could be deadly, though. Or maybe he just picked it up because he was near one of the boxes that dispense it into the water supply. Sachs, at the first or second scenes, in the tunnels? There were water pipes, right?'
'Water and, in one, sewage.'
'Incoming and outgoing,' joked Pulaski. Drawing laughs. From everyone except Rhyme.
'Any other
pipes - maybe some feeding chlorine into the mains?'
'I don't remember.'
'I want to find out. If this chlorine is from tap-water purification it's not helpful. If it's from a poison he's planning to use, then we can start checking sources.' Rhyme called up the pictures from the first two crime scenes. 'Let's get somebody back to the scenes and find out if there's a feeder line for the chemical.'
Sachs asked, 'Do you want Crime Scene to search?'
'No, just a uniform'll be fine,' Rhyme said. 'Anybody. But soon. Now.'
Sachs called Dispatch and had patrol cars sent to each of the two previous crime scenes, with instructions on what to look for.
Twenty minutes later Sachs's phone rang. She answered, then hit speaker.
'Okay, Officer, you're on with me and Lincoln Rhyme.'
'I'm at the Elizabeth Street scene, Detective. The Chloe Moore homicide.'
'Where are you exactly?' Rhyme asked.
'In the tunnel, next to the crime scene lamps and battery packs.'
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.'