‘So after the withdrawal, the professor never comes home. His wife reports him missing the next morning. The Houston PD traces his phone signal to a garbage dump in Louisiana and throws the case to the FBI since it crossed state lines. But we went to the dump, and the phone itself is nowhere to be found. Believe me, we did some digging.’ Thistle grimaces. ‘No phone, no car, no body. No one at the dump knows anything. No one at the college knows anything. None of his friends or family members know anything.’

This doesn’t sound like an especially weird case. Maybe Thistle just wanted to see me. I feel a dangerous little glow at the thought.

She looks at me expectantly. Apparently she’s ready for my input.

‘Are any of his contacts already known to the authorities?’ I ask.

‘None.’

‘Does he gamble?’

‘Everyone who knows him says no. I’ve been calling casinos, but no one has a record of him.’

‘Drugs?’

‘I found some pot at his home. Only a small amount—no sign that he was dealing. Nothing else suspicious in his apartment.’

‘Was it his birthday?’

Thistle sucks in air through her teeth. ‘How the hell did you guess that?’

Because I know how greedy people think. ‘Okay,’ I say, ‘he’s middle-aged, I assume, because he’s a math professor. Maybe having a mid-life crisis. Thinking about all the things he never got the chance to do before he got married and had kids—does he have kids?’

Thistle nods. ‘A daughter. Twenty-one.’

‘Right. So the message to the wife means he was going to do something after work, something he didn’t want her to know about. I thought it might be a birthday present to himself. If it’s not gambling or drugs, it’s sex. The amount of the ATM withdrawal narrows it down. Too large for a night out with his mistress, but too small to get far with a sex worker, too small to pay off a secret debt or to have someone killed—’

Thistle’s eyebrows go up. ‘Hold on, Blake. How many crimes are you planning to pin on our victim, exactly? And what kind of psycho has someone killed as a birthday present to themselves?’

‘I’m just showing you why I ruled those things out,’ I say. ‘My bet is he went to a strip club. Got drunk, bought himself a couple of lap dances. After the cash ran out and the booze wore off, he was disgusted with himself. Maybe started thinking about how the strippers are the same age as his daughter, or his students. Then he committed suicide.’

Thistle leans back in her chair. ‘That’s an inspiring story,’ she says. ‘Let’s leave aside for the moment that there are plenty of hitmen or sex workers who will perform their services for two hundred and sixty dollars—’