‘You were about to say, sir?’ But what? What? Providence? Provost? Prodigal? Problem?

Provost? No, no. Not provost. Protestant? Proprietor? A name or a title.

‘Nothing, John, nothing. I wonder if I’ve any clean cups . . .?’

A name or a title. Professor. Professor!

‘You weren’t about to mention a professor then?’

Watson’s lips were sealed. But Rebus was thinking fast now.

‘Professor Costello, for instance. He’s a friend of yours, isn’t he, sir? He doesn’t know Mr Jack then?’

Watson’s ears were turning red. Got you, thought Rebus. Got you, got you, got you. That coffee was worth every last penny.

‘Interesting though,’ mused Rebus, ‘that the Professor would know about a brothel.’

Watson slapped the desk. ‘Enough.’ His light morning mood had vanished. His whole face was red now, except for two small white patches, one on either cheek. ‘All right,’ he said. ‘You might as well know, it was Professor Costello who told me.’

‘And how did the Professor know?’

‘He said . . . he said he had a friend who’d visited the place one night, and now felt ashamed. Of course,’ Watson lowered his voice to a hiss, ‘there isn’t any friend. It’s the old chap himself. He just can’t bring himself to admit it. Well,’ his voice rising again, ‘we’re all tempted some time, aren’t we?’ Rebus thought of Gill Templer last night. Yes, tempted indeed. ‘So I promised the Professor I’d have the place closed down.’

Rebus was thoughtful. ‘And did you let him know when Operation Creeper was set for?’

It was Watson’s turn to be thoughtful. Then he nodded. ‘But he’s . . . he’s a professor . . . of divinity. He wouldn’t have been the one to tip off the papers. And he doesn’t know Gregor bloody Jack.’

‘But you told him? Date and time?’

‘More or less.’

‘Why? Why did he need to know?’

‘His “friend” . . . The “friend” needed to know so he could warn anyone he knew from going there.’

Rebus leapt to his feet. ‘Jesus Christ, sir!’ He paused. ‘With respect. But don’t you see? There was a friend. There was someone who needed to be warned. But not so they could stop their friends being caught . . . so they could ensure Gregor Jack walked straight into the trap. As soon as they knew when we were going in, all they had to do was phone Jack and tell him his sister was there. They knew he couldn’t not go and check it out for himself.’ He tugged open the door.

‘Where are you off to?’

‘To see Professor Costello. Not that I need to, not really, but I want to hear him say the name, I want to hear it for myself. Enjoy your coffee, sir.’

But Watson didn’t. It tasted like charred wood. Too bitter, too strong. For some time now he’d been wavering; now he made the decision. He’d stop drinking coffee altogether. It would be his penance. Just like Inspector John Rebus was his comforter . . .