They were starting with the assumption that the cause of death was poison but that wouldn’t be known until the medical examiner completed the analysis. Sachs had called and harangued the chief examiner to send over a preliminary report ASAP. They needed both the toxin and whatever sedative, as seemed likely, the perp had injected into Chloe to subdue her. Sachs had sealed the urgency by pointing out that they believed this murder was the start of a serial killing spree. The ME, she reported, had sounded as burdened as doctors generally do, especially city employee doctors, but he’d promised to move the Chloe Moore case to the front of the queue.

Again piqued by impatience, Rhyme said, ‘Sachs, you swabbed the site of the tattoo?’

‘Sure.’

‘Run that, Mel, and let’s see if we can get a head start on the poison.’

‘Will do.’ The tool Cooper used for this analysis was the gas chromatograph/mass spectrometer – two large, joined instruments sitting in the corner of the parlor. The gas chromatography portion of the equipment analyzes an unknown sample of trace by separating out each chemical it contains based on its volatility – that is, how long it takes to evaporate. The GC separates the component parts; the second device, the mass spectrometer, identifies the substances by comparing their unique structure with a database of known chemicals.

Running the noisy, hot machine – the samples are, in effect, burned – Cooper soon got results.

‘Cicutoxin.’

The NYPD had an extensive toxin database, which Rhyme had used occasionally when he’d been head of Investigation Resources – the old name for Crime Scene – though murder by poison was uncommon then and even more so now. Cooper scrolled through the entry for this substance. He paraphrased: ‘Comes from the water hemlock plant. Attacks the central nervous system. She’d have experienced severe nausea, vomiting, we can see frothing too. Muscle twitching.’ He looked up. ‘It’s one of the most deadly plants in North America.’

He nodded at the machine. ‘And it’s been distilled. No instances of that level of concentration ever recorded. Usually takes some time to die after it’s been administered. At these levels? She’d be dead in a half hour, little longer, maybe.’

‘What some famous Greek killed himself with, right?’ Pulaski asked.

Cooper said, ‘Not quite. Different strain of hemlock. Both in the carrot family, though.’

‘Who cares about Socrates?’ Rhyme snapped. ‘Let’s focus here. Does anyone else, aside from me, notice anything troubling about the source?’

Sachs said, ‘He could’ve found it in any field or swamp in the country.’

‘Exactly.’