`You know not what you do,' Rebus said to himself.

Some young mothers were crossing the football pitch. A crying baby was being shaken on its buggy springs. A toddler was being dragged screaming by the arm, his legs frozen in protest so that they scraped the ground. Both baby and toddler were being brought back into the Gar-b. But not without a fight.

Rebus didn't blame them for resisting.

Detective Sergeant Brian Holmes was in the Murder Room, handing a polystyrene cup of tea to Detective Constable Siobhan Clarke, and laughing about something.

`What's the joke?’

asked Rebus.

'The one about the hard-up squid,' Holmes answered.

`The one with the moustache?’

Holmes nodded, wiping an imaginary tear from his eye. `And Gervase the waiter. Brilliant, eh, sir?’

'Brilliant.’

Rebus looked around. The Murder Room was all purposeful activity. Photos of the victim and the locus had been pinned up on one wall, a staff rota not far from it. The staff rota was on a plastic wipe-board, and a WPC was checking names from a list against a series of duties and putting them on the board in thick blue marker-pen. Rebus went over to her. `Keep DI Flower and me away from one another, eh? Even if it means a slip of the pen.’

'I could get into trouble for that, Inspector.’

She was smiling, so Rebus winked at her. Everyone knew that having Rebus and Flower in close proximity, two detectives 'who hated one another, would be counter productive. But of course Lauderdale was in charge. It was Lauderdale's list, and Lauderdale liked to see sparks fly, so much so that he might have been happier in a foundry.

Holmes and Clarke knew what Rebus had been talking about with the WPC, but said nothing.

`I'm going back down Mary King's Close,' Rebus said quietly. `Anyone want to tag along?’

He had two takers.

Rebus was keeping an eye on Brian Holmes. Holmes hadn't tendered his resignation yet, but you never knew when it might come. When you joined the police, of course, you signed on for the long haul, but Holmes's significant other was pulling on the other end of the rope, and it was hard to tell who'd win the tug o' war.

On the other hand, Rebus had stopped keeping an eye on Siobhan Clarke. She was past her probation, and was going to be a good detective. She was quick, clever and keen. Police officers were seldom all three. Rebus himself might pitch for thirty per cent on a good day.

The day was overcast and sticky, with lots of bugs in the air and no sign of a dispersing breeze.

'What are they, greenfly?’

'Maybe midges.’

'I'll tell you what they are, they're disgusting.’

The windscreen was smeared by the time they reached the City Chambers, and there being no fluid in the wiper bottle, the windscreen stayed that way. It struck Rebus that the Festival really was a High Street thing. Most of the city centre streets were as quiet or as busy as usual. The High Street was the hub. The Chambers' small car park being full, he parked on the High Street. When he got out, he brought a sheet of kitchen-towel with him, spat on it, and cleaned the windscreen.

`What we need is some rain.’

'Don't say that.’

A transit van and a flat-back trailer were parked outside the entrance to Mary King's Close, evidence that the builders were back at work. The butcher's shop would still be taped off, but that didn't stop the renovations.

'Inspector Rebus?’

An old man had been waiting for them. He was tall fit looking and wore an open cream-coloured raincoat despite the day's heat. His hair had turned not grey silver but a kind of custard yellow, and he wore half-moon glasses most of the way down his nose, as though he needed them only to check the cracks in the pavement.

'Mr Blair-Fish?’

Rebus shook the brittle hand.

'I'd like to apologise again. My great-nephew can be such a 'No need to apologise, sir. Your great-nephew did us a favour. If he hadn't gone down there with those two lassies, we wouldn't have found the body so fast as we did. The quicker the better in a murder investigation.’

Blair-Fish inspected his oft-repaired shoes, then accepted this with a slow nod. 'Still, it's an embarrassment.’

'Not to us, sir.’

'No, I suppose not.’

'Now, if you'll lead the way…?’

Mr Blair-Fish led the way.

He took them in through the door and down the flights of stairs, out of daylight and into a world of low-wattage bulbs beyond which lay the halogen glare of the builders. It was like looking at a stage-set. The workers moved with the studied precision of actors. You could charge a couple of quid a time and get an audience, if not a Fringe First Award. The gaffer knew police when he saw their, and nodded a greeting. Otherwise, nobody paid much attention; except for the occasional sideways and appraising glance towards Siobhan Clarke. Builders were builders, below ground as above.

Blair-Fish was providing a running commentary. Rebus reckoned he'd been the guide when the constable had come on the tour. Rebus heard about how the close had been a thriving thoroughfare prior to the plague, only one of many such plagues to hit Edinburgh. When the denizens moved back, they swore the close was haunted by the spirits of those who had perished there. They all moved out again and the – street fell into disuse. Then came a fire, leaving only the first few storeys untouched. (Edinburgh tenements back then could rise to a precarious twelve storeys or more.) After which, the city merely laid slabs across what remained and built again, burying Mary King's Close.

`The old town was a narrow place, you must remember, built along a ridge or, if you enjoy legend, on the back of a buried serpent. Long and narrow. Everyone was squeezed together, rich and poor living cheek by jowl. In a tenement like this you'd have your paupers at the top, your gentry in the middle floors, and your artisans and commercial people at street level.’

`So what happened?’ asked Holmes, genuinely interested.

`The gentry got fed up,' said Blair-Fish. `When the New Town was built on the other side of Nor' Loch, they were quick to move. With the gentry gone, the old town became dilapidated, and stayed that way for a long time.’

He pointed down some steps into an alcove. 'That was the baker's. See those flat stones? That's where the oven was. If you touch them, they're still warmer than the stones around them.’

Siobhan Clarke had to test-this. She came back shrugging. Rebus was glad he'd brought Holmes and Clarke with him. They kept Blair-Fish busy while he could keep a surreptitious eye on the builders. This had been his plan all along: to appear to be inspecting Mary King's Close, while really inspecting the builders. They didn't look nervous; well, no more nervous than you would expect. They kept their eyes away from the butcher's shop, and whistled quietly as they worked. They did not seem inclined to discuss the murder. Someone was up a ladder dismantling a run of pipes. Someone else was mending brickwork at the top of a scaffold.

Further into the tour, away from the builders, Blair-Fish took Siobhan Clarke aside to show her where a child had been bricked up in a chimney, a common complaint among eighteenth-century chimney sweeps.

‘The Farmer asked a good question,’ Rebus confided, to Holmes. 'He said, why would you bring anyone down here Think about it. It shows you must be local. Only locals know about Mary King's Close, and even then only a select few.’

It was true, the public tour of the close was not common knowledge, and tours themselves were by no means frequent.

'They'd have to have been down here themselves, or know someone who had. If not, they'd more likely get lost than find the butcher's.’

Holmes nodded. `A shame there's no record of the tour parties.’