‘Setting a trap with human bait,’ he said quietly, each word chipped from Aberdeen granite, his bald head gleaming under the lights of MIR-1, ‘was never the plan.’

‘Change of plan,’ said Swire.

‘I’m not wearing a bullet-proof vest,’ Scarlet Bush was telling DI Whitestone. ‘Bob was very specific: “Come alone. No tapes I can’t see.” He might think a bullet-proof vest is a wire. I’m not wearing it.’

‘It’s not a bullet-proof vest,’ Whitestone said patiently, ‘it’s a Kevlar Stealth. Lightweight, the thinnest we have. Invisible under the clothes you’re wearing. I’d wear it if I were you.’

Gane’s laptop was open on Bob the Butcher’s timeline. Bob had changed his picture again. Instead of Robert Oppenheimer’s thoughtful, pipe-smoking skull, there was now a mushroom cloud.

In sleep – in confusion – in the depths of shame – the good deeds a man has done before defend him. #killallpigs

‘Where’s his response?’ I said.

‘He didn’t respond online,’ Gane said. ‘He called her.’ He laughed. ‘On a telephone. A landline.’

Gane grinned, and I saw that Cho and his techie pals from the PCeU were looking sour.

‘Stick around, boys!’ Gane said. ‘We might be able to show you a few tricks!’

‘Give DI Gane your phone and he’ll fit a GPS tracking device,’ Whitestone told Bush.

‘I don’t want to carry anything bulky,’ the journalist said.

‘It’s either a SIM card or some software,’ Gane said, cutting her off. ‘You’re not going to notice it. The only people who will know it’s even there are us, OK? But it means we know where you are. It means we can pinpoint your movements to within ten metres. If you go beyond a prescribed area, it sends us an alarm.’

Bush gave Gane her phone.

‘The Kevlar Stealth and the tracking device,’ she said. ‘Is that it?’

Whitestone nodded. ‘That’s it. Belt and braces.’

‘What did Bob say to you?’ I said.

I saw the pride in the journalist’s eyes.

‘He said he liked my piece,’ she said. ‘And he said he’d be in touch.’

‘How do you know it was him?’

‘He told me he would post an Oppenheimer quote in the Bob the Butcher timeline. “In sleep – in confusion – in the depths of shame – the good deeds a man has done before defend him.” And then he did.’