Pam nodded and rubbed compulsively again. ‘He was telling me all these terrible things. He was, it sounded like he was planning to be a new Hitler. He was going to kill his aunt and uncle and start his own militia movement. You know, Mom wasn’t really all that smart. She’d ramble on and on and you couldn’t take her seriously. But Billy, he was in a different league. He’d been to college. He was going to start schools and indoctrinate kids. He talked about the Rule of Skin. I could see he was obsessed with it. Racism, pure and simple.’

‘Rule of Skin,’ Rhyme mused. It certainly jibed with the manifesto they planned to leave at the site of poisoning at the water pipe. He thought back to what Terry Dobyns had told them.

If you can find out why he’s so fascinated with skin, that’s key to understanding the case …

Pam continued, ‘And he’d been obsessing about me all these years.’ She explained about the betrothal, about Billy’s coming here a year ago to start planning his attack on the city – and his seduction of her. Pam shivered.

‘Do you want to get in the van?’ Rhyme asked, nodding toward the accessible vehicle Thom had driven here. Her place was sealed for the crime scene search and Pam was clearly cold; her nose and eyes red, fingertips too.

‘No,’ Pam said quickly. She seemed more comfortable with the sunlight, despite the frigid air. ‘You caught them all?’

‘Everybody who was here in New York, it seems,’ Rhyme explained. ‘Matthew and Harriet Stanton. Their son, Joshua.’

The search team had found a real ID on the unsub’s body. William Haven, twenty-five. A tattoo artist who lived in South Lakes, Illinois.

Rhyme continued, ‘We have people going through all of their documents now, notes, phones, computers. We’ve got a few conspirators in Southern Illinois but there’ll be others. The bombs weren’t set to detonate but they were real: gunpowder, detonators and cell phone triggers. Somebody who knew what they were doing put the IEDs together.’

‘If they were anything like my mother’s underground group, the Patriot Frontier, there’d be dozens of people involved. They were always meeting late at night, sitting in kitchens, drinking coffee, making their fucking little plans …

Lincoln?’ Pam asked.

He raised an eyebrow.

‘How did you know? About Seth? To send the police here?’

‘I didn’t know. But I suspected it when it occurred to me: How did the unsub know about TT Gordon?’

‘Who?’

‘The tattoo artist that you and Seth met in my lab.’

‘Oh, the guy with the weird beard and the piercings.’