It was a straightforward case of theft. Professor James Aloysius Costello was Professor of Divinity at the University of Edinburgh. One day someone had walked into his office, then walked out again taking with them several rare books. Priceless, according to the Professor, though not to the city's various booksellers and auction rooms. The list seemed eclectic: an early edition of Knox's Treatise on Predestination, a couple of Sir Walter Scott first editions, Swedenborg's Wisdom of Angels, a signed early edition of Tristram Shandy, and editions of Montaigne and Voltaire.

None of which meant much to Rebus until he saw the estimates at auction, provided by one of the George Street auction houses. The question then was: what were they doing in an unlocked office in the first place?

'To be read,' answered Professor Costello blithely. 'To be enjoyed, admired. What good would they be locked up in a safe or in some old library display case?'

'Did anyone else know about them? I mean, about how valuable they are?'

The Professor shrugged. I had thought, Inspector, that I was amongst friends.'

He had a voice like a peat bog and eyes that gleamed like crystal. A Dublin education, but a life spent, as he put it, 'cloistered' in the likes of Cambridge, Oxford, St Andrews, and now Edinburgh. A life spent collecting books, too. Those left in his office – still kept unlocked – were worth at least as much as the stolen volumes, perhaps more.

'They say lightning never strikes twice,' he assured Rebus.

'Maybe not, but villains do. Try to lock your door when you step out, eh, sir? If nothing else.'

The Professor had shrugged. Was this, Rebus wondered, a kind of stoicism? He felt nervous sitting there in the office in Buccleuch Place. For one thing, he was a kind of Christian himself, and would have liked to be able to talk the subject through with this wise-seeming man. Wise? Well, perhaps not worldly-wise, not wise enough to know how snib locks and human minds worked, but wise in other ways. But Rebus was nervous, too, because he knew himself for a clever man who could have been cleverer, given the breaks. He had never gone to university, and never would. He wondered how different he would be if he had or could…