‘Meaning whoever left that first one, back in nineteen seventy-two, also left one for Philippa Balfour?’

Rebus nodded again.

‘If anyone can do it, John, you can. I’ve always had confidence in your sheer pig-headedness and inability to listen to your senior officers.’

Rebus placed his cup back on its saucer. ‘I’ll take that as a compliment,’ he said. Looking around the room again, preparing to rise and make his farewells, he was struck by something. This house was the only thing the Farmer controlled now. He brought order to it the way he’d controlled St Leonard’s. And if he ever lost the will power or the ability to keep it in shape, he’d curl up his toes and die.

‘This is hopeless,’ Siobhan Clarke said.

They’d spent the best part of three hours in the Central Library, followed by nearly fifty quid at a bookshop, buying maps and touring guides of Scotland. Now they were in the Elephant House coffee-shop, having commandeered a table meant for six. It was right below the window at the back of the café, and Grant Hood was staring out at the view of Greyfriars Churchyard and the Castle.

Siobhan looked at him. ‘Have you switched off ?’

He kept his eyes on the view. ‘You have to sometimes.’

‘Well, thanks for your support.’ It came out more huffily than she’d expected.

‘Best thing you can do,’ he went on, ignoring her tone. ‘There are days when I get stuck with the crossword. I don’t go knocking my brains out. I just put it to one side and pick it up again later. And often I find that one or two answers come to me straight away. Thing is,’ now he turned towards her, ‘you fix your mind on a certain track, until eventually you can’t see all the alternatives.’ He got up, walked over to where the café kept its newspapers, and came back with that day’s Scotsman. ‘Peter Bee,’ he said, folding it so the crossword on the back page was uppermost. ‘He’s cryptic, but doesn’t depend on anagrams the way some of the others do.’

He handed her the paper and she saw that Peter Bee was the name of the crossword’s compiler.

‘Twelve across,’ Grant said, ‘he had me looking for the name of an old Roman weapon. But all it was in the end was an anagram.’

‘Very interesting,’ Siobhan said, tossing the paper on to the table, where it covered the half-dozen map-books.

‘I’m just trying to explain that sometimes you have to clear your mind for a while, start again from scratch.’

She glared at him. ‘Are you saying we’ve just wasted half the day?’

He shrugged.