‘No. She’s rebooted a few times, but hasn’t left it switched off for more than a couple of minutes since she acquired it two years ago.’

‘Can you see where she was on March nineteenth?’

Vasquez brings it up. ‘Three addresses. One is her home, one is a shopping centre, and the third …’ He types up a quick search. ‘The third one is a condemned apartment building. Can’t tell you which unit she was in.’

‘How long has it been condemned?’

‘Three years.’

Which means Black only thought she was visiting the home of the wigmaker. Or she was lying to us.

‘Okay,’ I say. ‘What about her freelance career?’

Vasquez brings up Black’s profile on the job site. ‘She did all the jobs she said she did—at least, she accepted them, got paid for them and got excellent public feedback for them.’

‘No doubt,’ Thistle says drily. ‘How about Luxford’s computer?’

‘Still nothing. The letters on the post-it note weren’t the password, and I can’t decrypt the hard drive without it. Any other ideas for what it might be?’

Thistle shakes her head.

‘Show me the computer again,’ I say.

Vasquez leads us over to one of the computers, which I recognise as the one from Shannon’s place.

‘It looks like he’s used AES-256 to encrypt the hard drive,’ he says. ‘It’s a symmetric encryption algorithm that uses a block cipher, so I’ll never break it with today’s technology.’

‘But it was encrypted with current tech, right?’ Thistle says. ‘Luxford isn’t a visitor from the future?’

Vasquez doesn’t laugh. ‘Decryption is always years behind encryption. That’s what makes encryption useful for criminals, and a pain in the ass for us. But Luxford’s ISP is cooperating, so we know he used Tor. You know about Tor?’

‘Yes,’ Thistle says.

‘No,’ I say, not wanting to appear too knowledgeable. I used to sell credit card numbers on the dark web.

‘It’s a secure web browser originally developed by the navy,’ Vasquez says. ‘Typically, when you’re browsing with Tor, the only thing an outsider can tell is that you’re using Tor. They can’t tell what sites you’re visiting or what you’re doing on them.’

‘The navy released it to the public, right?’ Thistle says.

Vasquez nods. ‘So they could use it without anyone knowing it was them. Anyway, Tor gets you to the dark web. Which is where you go if you want to tip off a journalist about NSA wiretapping. Or to buy drugs, or hire a hit man, or look at child pornography.’

‘So what was Luxford doing?’

‘I don’t know. He accessed the dark web only twice, almost a year ago. My best guess, based on Abbey Chapman’s testimony, is that he made a friend there, and then started swapping videos with the friend by mail.’

Fred.