She’d thought about this. ‘True. If they’d really wanted to rupture the pipes they’d use shaped charges. Armor piercing. Of course they would.’

‘Exactly. He wanted us to find the bombs. And – with the Bible verses – wanted us to believe the target was the water mains. Why?’

They’d answered nearly simultaneously. ‘To shut down the supply.’

Shutting off the water flow by closing the main valves would be only temporarily disruptive.

‘Who cares? That couldn’t be the motive,’ Rhyme had said.

Then he’d offered: But what would make sense was to trick the city into shutting off the supply to lower the pressure. Which would allow their unsub to drill into the pipe and introduce a poison into the line. He’d then plug the hole; Rhyme had reminded the team about the welding material evidence found at the Chloe Moore crime scene.

And the poison, Rhyme had concluded, would be botulinum – since they’d found traces of the material from cosmetic surgical supply houses and the Botox syringes. Rhyme had thought the plastic surgery evidence meant their unsub was planning on changing his appearance. But it was possible too that the purpose of the break-in was to steal botulinum, whose spores were maintained by medical operations specializing in plastic surgery products and supplies. He’d decided botulinum had to be the poison; no other toxin was powerful enough to cause widespread devastation.

Rhyme had called his FBI contact, Fred Dellray, and City Hall and explained what he suspected. The mayor and police chief had in turn ordered the DEP to announce that it was shutting down the water supply for a few hours. In fact, they kept the system fully operational – which because of the pressure would prevent anything from being introduced into the pipes. The DEP would use the grid sensors to pinpoint any leaks, telling the NYPD exactly where the unsub had cut into the line.

As she sat impatiently behind the wheel of her car, the engine growling, Sachs’s phone rang once more. It was Rhyme. ‘Where are you, Sachs?’

‘Almost at the spot DEP gave us.’

‘Listen to me.’

‘What else would I be doing?’ she muttered. And concentrated on avoiding an idiot of a bicyclist.

Rhyme continued, ‘I’ve just been on the phone with the Centers for Disease Control in Atlanta. We conferenced – forgive the verb – with Homeland Security and the bio-chem weapons people at Fort Detrick. It’s worse than I thought. Don’t go into the access room. We’re getting a tactical hazmat team together.’

‘I’m here, Rhyme. Now. I can’t just sit around and wait. The unsub’s right underneath me.’

She pulled the muscle car up on the sidewalk, scooting pedestrians out of the way. They complied; she looked far too fierce to argue.

Rhyme continued, ‘I just realized that this isn’t ordinary botulinum.’

‘Now, that’s a phrase you don’t hear every day, Rhyme.’