Chib Calloway waited in the foyer for a couple of minutes, but the only other arrivals were a middle-aged couple with Australian accents and leathery skin. He pretended to be studying a floor plan of the building, then gave a twitch of the mouth, signalling to the guards that he was quite satisfied with arrangements. Taking a deep breath, he walked inside.

It was quiet in the gallery. Bloody big rooms, too, echoing with coughs and whispers. He saw the Aussies again, plus some overseas students who were being taken round by a guide. No way they were locals – too tanned, too fashion-conscious. They shuffled slowly, near-silently past the huge canvases, looking bored. Not too many guards in here. Chib craned his neck, seeking out the all-seeing CCTV cameras. They were just where he thought they’d be. No wires trailing from the paintings, though, meaning no alarms. Some of them looked fixed to the walls by screws, but by no means all of them. Even if they were, thirty seconds with a Stanley knife and you’d have what you came for… most of it, anyway. The canvas, if not the frame. Half a dozen pensioners in uniforms – no problem at all.

Chib sat himself down on an upholstered bench in the middle of one of the rooms and felt his heart rate begin to slow. He pretended to be interested in the painting opposite, a landscape with mountains and temples and sunbeams. There were a few figures in the foreground, dressed in flowing white robes. He’d no idea what any of it was supposed to mean. One of the foreign students – a bronzed, Spanish-looking lad – blocked his view for a moment before moving to the side to check out the information panel on the wall, oblivious to Chib’s glare: Hey, pal, this is my painting, my city, my country…

Another man walked into the room: older than the student and better dressed. A black woollen overcoat fell to just above his feet. His shoes were black, glossy and unscuffed. He carried a folded newspaper and looked like he was just killing time, cheeks puffed out. Chib gave him the stare all the same, and decided he knew the face from somewhere. His stomach clenched – was this whoever’d been tailing him? Didn’t look like a villain, but then he didn’t look much like a cop either. Where had Chib seen him before? The visitor had given the painting the briefest of glances, and was heading away, brushing past the student. He was already out of the room by the time Chib placed him.

Chib got to his feet and made to follow.

Mike Mackenzie had recognised the gangster straight away, hoping it wasn’t too obvious when he exited the room pronto. This collection wasn’t really his thing anyway; he’d only come into town to do a bit of shopping: shirts to start with (not that he’d found any he liked). Then some eau de cologne and a slight detour into Thistle Street and Joseph Bonnar’s jewellery shop. Joe specialised in nice antique pieces, and Mike had gone there with Laura in mind. He’d been thinking of that opal around her neck, imagining her wearing something different, something unusual.

Something bought by him.

But though Joe was a master of his craft – Mike had a pocket watch back home to prove it – he hadn’t managed to work his charms this time. Mainly because it had suddenly dawned on Mike: what the hell am I doing? Would Laura thank him for the gesture? What exactly would she read into it? Did she even like amethysts and rubies and sapphires?

‘Call again, Mr Mackenzie,’ Bonnar had said, opening the door for him. ‘It’s been too long.’

So: no shirts and no jewellery. One o’clock had found him on Princes Street, not quite hungry enough for lunch and within a stone’s throw of the National Gallery. His mind felt clogged; hard to say why he’d been drawn to the place. There were some nice pieces – he’d be the first to acknowledge as much – but it was all a bit stuffy and reverential. ‘Art is good for you,’ the collection seemed to be saying. ‘Here, have some.’

The past few days, he’d been mulling over Professor Gissing’s argument about art as collateral. He wondered what percentage of the world’s art was actually kept in bank vaults and the like. Like unread books and unplayed music, did it matter that art went unseen? In a generation’s time, it would still be there, awaiting rediscovery. And was he himself any better? He’d visited regional galleries and viewed their collections, knowing he had better examples of some of the artists hanging on his walls at home. Wasn’t each home and living room a private gallery of sorts?

Help some of those poor imprisoned paintings to escape.

Not from public galleries, of course, but from wall safes and bank vaults and the unvisited rooms and corridors of all those corporate buyers. First Caledonian Bank, for example, had a portfolio running into the tens of millions – most of the usual suspects (they even boasted an early Bacon), plus the cream of new talent, snapped up at all those annual degree shows around the UK by the bank’s portfolio curator. Other companies in Edinburgh owned their own hauls and were sitting tight on them, the way a miser would sit on a mattress filled with cash.

Mike was wondering: maybe if he made a gesture. Opened a gallery and placed his own collection there… could he persuade others to join him? Talk to First Caly and all the other big players. Make a thing of it. Maybe that was why he’d felt drawn to the National Gallery – the perfect place to do a little more thinking on the subject. The last person he’d expected to see was Chib Calloway. And now, turning around, here was Calloway stalking towards him, smile fixed but eyes hard and unblinking.

‘You keeping tabs on me?’ the gangster growled.

‘Wouldn’t have taken you for a patron of the arts,’ was all Mike could think of by way of an answer.

‘Free country, isn’t it?’ Calloway bristled.

Mike flinched. ‘Sorry, that came out all wrong. My name’s Mike Mackenzie, by the way.’ The two men shook hands.

‘Charlie Calloway.’

‘But most people call you Chib, right?’

‘You know who I am, then?’ Calloway considered for a moment and then nodded slowly. ‘I remember now – your pals couldn’t look at me, but you held eye contact throughout.’

‘And you pretended to shoot me as you drove away.’

Calloway offered a grudging smile. ‘Least it wasn’t the real thing, eh?’

‘So what brings you here today, Mr Calloway?’

‘I was just remembering that book of paintings, the one you lot were poring over in the bar. I take it you know about art, Mike?’

‘I’m learning.’

‘So… this one we’re standing beside…’ Calloway took a step back. ‘Guy on a horse, so far as I can see. Not a bad likeness.’ He stuffed his hands in his pockets. ‘How much would it fetch?’

‘Unlikely it would ever come to auction.’ Mike gave a shrug. ‘Couple of million?’ he guessed.

‘Hell’s teeth.’ Calloway moved along to the next painting. ‘And this one here?’

‘Well, that’s a Rembrandt… tens of millions.’

‘Tens!’

Mike looked around. A couple of the liveried custodians were beginning to take an interest. He gave them his most winning smile and started to move away in the opposite direction, Calloway catching him up only after a few more seconds of staring at the Rembrandt self-portrait.

‘It’s not really about the money, though, is it?’ Mike heard himself say, even though he knew only a part of him really believed that.

‘Isn’t it?’

‘What would you rather look at – a work of art, or a framed selection of banknotes?’

Calloway had retrieved one of his hands from its pocket, and he was now rubbing the underside of his chin. ‘I’ll tell you what, Mike – ten million in cash wouldn’t be on the wall long enough to find out.’

They shared a laugh and Calloway ran his free hand across the top of his head. Mike began to wonder about the other hand – the one in the pocket. Was it holding a gun? A knife? Had Calloway come in here with something other than browsing in mind?