'Hacking?’

'They probably used the stuff in her shop. They hacked into Army and police computers, bypassed security, invaded datafiles, then marched out again without leaving any trace.’

'So what did they do?’

Murdock was talking now, enjoying the release. He wiped tears from below his glasses. 'They monitored a couple of police investigations and altered a few inventories. Believe me, once they were in, they could have done a lot more.’

The way Murdock went on to explain it, it was almost ludicrously simple. You could steal from the Army (with inside assistance, there had to be inside assistance), and then erase the theft by altering the computer records to show stocks as they stood, not as they had been. Then, if SCS or Scotland Yard or anyone else took an interest, you could monitor their progress or lack of it. Millie: Millie had been the key throughout. Whether or not she knew what she was doing, she got Billy Cunningham in. He placed her in the lock and turned. The disk had contained instructions on their hacking procedures, tips for bypassing security checks, the works.

Rebus didn't doubt that the further Billy Cunningham got in, the more he wanted out. He'd been killed because he wanted out. He'd probably mentioned his little insurance policy in the hope they would let him leave quietly. Instead, they'd tried to torture its whereabouts out of him, before delivering the final silencing bullet. Of course, The Shield knew Billy wasn't hacking alone. It wouldn't have taken them long to get to Millie Docherty. Billy had stayed silent to protect her. She must have known. That's why she'd run.

'There was stuff about this group, too, The Shield,' Murdock was saying. 'I thought they were just a bunch of hackers.’

Rebus tried him with a few names. Davey Soutar and Jamesie MacMurray hit home. Rebus reckoned that in an interview room he could crack Jamesie like a walnut under a hammer. But Davey Soutar… well, he might need a real hammer for that. The final file on the computer was all about Davey Soutar and the Gar-B.

'This Soutar,' Murdock said, 'Billy seemed to think he'd been skimming. That was the word he used. There's some stuff stashed in a lock-up out at Currie.’

Currie: the lock-up would belong to the MacMurrays.

Murdock looked at Rebus. 'He didn't say what was being skimmed. Is it money?’

'I underestimated you, Davey,' Rebus said aloud. 'All down the line. It might be too late now, but I swear I won't underestimate you again.’

He thought of how Davey and his kind hated the Festival. Hated it with a vengeance. He thought of the anonymous threats.

'Not money, Mr Murdock. Weapons and explosives. Come on, let's get out of here.’

Jamesie talked like a man coming out of silent retreat, especially when his father, hearing the story from Rebus, ordered him to. Gavin MacMurray was incensed, not that his son should be in trouble, but that the Orange Loyal Brigade hadn't been enough for him. It was a betrayal.

Jamesie led Rebus and the other officers to a row of wooden garages on a piece of land behind MacMurray's Garage. Two Army men were on hand. They checked for booby traps and trip wires and it took them nearly half an hour to get round to going in. Even then, they did not enter by the door. Instead, they climbed a ladder to the roof and cut through the asphalt covering, then dropped through and into the lock-up. A minute later, they gave the all clear, and a police constable broke open the door with a crowbar. Gavin MacMurray was with them.

'I haven't been in here for years,' he said. He'd said it before, as if they didn't believe him. 'I never use these garages.’

They had a good took round. Jamesie didn't know the precise location of the cache, only that Davey had said he needed a place to keep it. The garage had operated as a motorcycle workshop – that was how Billy Cunningham had got to know Jamesie, and through him Davey Soutar, in the first place. There were long rickety wooden shelves groaning with obscure metal parts, a lot of them rusted brown with age, tools covered with dust and cobwebs, and tins of paint and solvent. Each tin had to be opened, each tool examined. If you could hide Semtex in a transistor radio, you could certainly hide it in a tool shed. The Army had offered a specialised sniffer dog, but it would have to come from Aldershot. So instead they used their own eyes and noses and instinct.

Hanging from nails on the walls were old tyres and wheels and chains. Forks and handlebars lay on the floor along with engine parts and mouldy boxes of nuts, bolts and screws. They scraped at the floor, but found no buried boxes. There was a lot of oil on the ground.

'This place is clean,' said a smudged Army man. Rebus nodded agreement.

'He's been and cleared the place out. How much was there, Jamesie?’

But Jamesie MacMurray had been asked this before, and he didn't know. 'I swear I don't. I just said he could use the space. He got his own padlock fitted and everything.’

Rebus stared at him. These young hard men, Rebus had been dealing with them all his life and they were pathetic, like husks in suits of armour. Jamesie was about as hard as the Sun crossword. 'And he never showed you?’

Jamesie shook his head. 'Never.’

His father was staring at him furiously. 'You stupid wee bastard,' Gavin MacMurray said. 'You stupid, stupid wee fool.’

'We'll have to take Jamesie down the station, Mr MacMurray.’

'I know that.’

Then Gavin MacMurray slapped his son's face. With a hand callused by years of mechanical work, he loosened teeth and sent blood curdling from Jamesie's mouth. Jamesie spat on the dirt floor but said nothing… Rebus knew Jamesie was going to tell them everything he knew.

Outside, one of the Army men smiled in relief. 'I'm glad we didn't find anything.’

‘Why?’ 'Keeping the stuff in an environment like that, it's bound to be unstable.’

'Just like the guy who's got it.’

Unstable… Rebus thought of Unstable from Dunstable, confessing to the St Stephen Street killing, raving to DI Flower about curry and cars… He walked back into the garage and pointed to the stain on the floor.

'That's not oil,' he said, 'not all of it.’

'What?’

'Everybody out, I want this place secured.’

They all got out. Flower should have listened to Unstable from Dunstable. The tramp had been talking about Currie, not curry. And he'd said cars because of the garages. He must have been sleeping rough nearby and seen or heard something that night.

'What is it, sir?’

one of the officers asked Rebus.

`If I'm right, this is where they killed Calumn Smylie.’

That evening, Rebus moved out of the hotel and back into Patience's flat. He felt exhausted, like a tool that had lost its edge. The stain on the garage floor had been a mixture of oil and blood. They were trying to separate the two so they could DNA-test the blood against Calumn Smylie's. Rebus knew already what they'd find. It all made sense when you thought about it.

He poured a drink, then thought better of it. Instead he phoned Patience and told her she could come home in the next day or two. But she was determined to return in the morning, so he told her why she shouldn't. She was very quiet for a moment.

'Be careful, John.’

`I'm still here, aren't I?’

'Let's keep it that way.’

He rang off when he heard the doorbell. The manhunt for Davey Soutar was in full swing, under the control of CI Lauderdale at St Leonard's. Arms would be issued as and when necessary. Though they didn't know the extent of Soutar's cache, no chances would be taken. Rebus had been asked if he'd like a bodyguard.

'I'll trust to my guardian angel,' he'd said.

‘The doorbell rang again. He felt naked as he walked down the long straight hall towards the door. The door itself was inch-and-a-half thick wood, but most guns could cope with that and still leave enough velocity in the bullet to puncture human flesh. He listened for a second, then put his eye to the spy-hole. He let his breath out and unlocked the door.