‘He was a math professor. I doubt he believed in giants. But …’ I trail off, thinking.

‘What?’

‘If you wanted to simulate a sex act with a giant, how would you do it?’

‘I sure hope that’s rhetorical,’ Thistle says.

Before I can explain, Vasquez is back. ‘Guys,’ he says, ‘I got something.’

We both turn. Vasquez doesn’t look excited. In fact, his face is grim.

‘I programmed the computer to include Ruthven’s dating app in its search patterns. It couldn’t find anything on the dates you gave me. But something else came up.’

‘What?’ Thistle asks.

‘Sixteen missing men over the last eleven months, all from Houston, all using the same app.’

I quickly count the bodies I’ve disposed of for Charlie Warner. It’s easy to lose track, since I destroy all evidence of each one—I think this is why some killers keep trophies—but I don’t think it’s sixteen yet.

‘How popular is the app?’ I ask. Sixteen sounds like a lot, but Houston is a city of more than two million people.

‘Forty-six thousand users in the city. But these are all white, heterosexual males of the same approximate age, height and weight. The computer thinks it’s significant.’

Those don’t sound like Charlie Warner’s victims. This is something entirely new. Thistle and I look at one another.

‘Holy shit,’ she breathes. ‘We have a fucking serial killer on our hands.’

‘And he has a type,’ I say.

CHAPTER 18

CHAPTER 18

What is the only organ that named itself?

‘How long can we keep this quiet?’ I ask.

Thistle and I are in the world’s slowest elevator, on our way back up to the ground floor. Vasquez is on the phone to the director, telling her what he’s found. A serial killer is a major hassle for the FBI. I’m glad I’m not the one who has to break the news to her.

If the victims were women or children, we wouldn’t be assuming that they were dead. There are 46 million slaves in the world, 58,000 of them in the USA. Many missing people are eventually found in illegal brothels, small factories or private dungeons. But few of those slaves are white adult males. No one at the FBI thinks these seventeen men will be found alive, especially not the civilian consultant who’s currently digesting one of the victims.

When Vasquez ends the call, he’ll adjust his algorithm, looking for other connections between the victims. Maybe we’ll get lucky and find a clue about where the perp lives, or where he works. Or, if it’s Shannon, where he is now.

‘We can’t keep it quiet,’ Thistle says. ‘We have to make a statement.’

‘Legally?’

‘Ethically. People have a right to know if there’s a serial killer around.’

‘But then he’ll know we’re after him,’ I say. ‘He’ll skip town.’