‘Police,’ Gallo called, waving his badge at the astonished museum staff as they burst through the entrance and bypassed the queue waiting patiently at the ticket desk.

Allegra sprinted through first one room, then another, her eyes skipping over the paintings, not entirely sure where it was, but knowing it was here somewhere. Filippo Lippi, Piero de Cosimo…no, not here. Next room. Tintoretto, Bronzino…still nothing. Carry on through. Guercino…

‘There,’ she called triumphantly, pointing at the wall.

‘Ammàzza!’ Gallo swore, stepping past her for a closer look.

The large painting showed a bearded man being decapitated by a woman, a sword in her right hand, his hair firmly gripped in her left. He was naked, his face contorted into an inhuman scream, his body convulsed by pain, the blood spurting on to a white sheet. Next to the woman stood an old woman, her wrinkled face hungrily absorbing the man’s death, her hands gripping the hem of her mistress’s dress to keep it clear of the blood.

Gallo held the photograph of the Pantheon crime scene up next to it. There was no question it had been staged to mirror the painting’s composition.

‘It’s the same.’

‘Judith and Holofernes,’ Allegra said slowly. ‘It was only when I saw the photos that I made the connection.’

‘And Ricci?’

‘The Crucifixion of Saint Peter in the Cerasi Chapel in Santa Maria del Popolo,’ she confirmed. ‘That’s what links your two murders, Colonel. The killers are re-enacting scenes from Caravaggio paintings.’

Amalfi Casino and Hotel Resort, Las Vegas

17th March – 11.56 p.m.

Tom had insisted on getting down on to the floor early, guessing that whoever had been sent to meet him would already be in position and that it would help if it looked as though he was keen to do the deal. More importantly, it gave them a chance to see the money, to see that this was for real. It was at Tom’s feet now – twenty million in cash, neatly packed into two aluminium suitcases.

Twenty million dollars.

There was a time, perhaps, when he might have considered…But those days were behind him now, although you wouldn’t have guessed it from the obvious reluctance with which Stokes had entrusted the cases to him, and his pointed reminder that they were electronically tagged. Then again, maybe Tom was nałve to have expected anything else. All Stokes had to go on was his file, and that told its own, damning story.

He looked around the blinking, cavernous floor to get his bearings, momentarily disoriented by the tumbrel-clatter of the roulette wheels, the dealers’ barked instructions and the machines’ remorseless chuckling. The place was packed. If Vegas was suffering from the economic slowdown that the press had been so gleefully reporting for the past few months, then it was hiding it well. Either that or it was still in denial.

He spotted Jennifer at the bar to his left, nursing a coke. Ortiz, meanwhile, was to his right, pretending to play video poker and losing badly. Stokes, he knew, was in the back with the casino’s head of security, watching the screens and coordinating the other agents who had been posted around him. In front of him was a roulette table, the animated abandon with which a noticeably younger crowd were merrily flinging chips on to the baize contrasting with the silent, mesmerised application of the older people on the slots.

On cue, a woman wearing an ‘I love Fort Lauderdale’ T-shirt waddled over to the machine next to him, the stool screeching under her weight. Resting a bucket full of quarters on her lap, she bowed her head briefly as if offering up a prayer, and then began to feed it with metronomic precision, the tips of her fingers stained black by the coins. A kaleidoscope of changing colours immediately skipped across her rapt face, her eyes gazing up at the spinning wheels with a mixture of hope and expectation.

Tom wondered if she knew that her faith was unlikely to be rewarded. In here, chance danced to the casino’s tune. The roulette tables that paid out thirty-five to one, when the odds of winning were one in thirty-seven. The deliberate location of the premium slots next to the main aisles and blackjack tables, to lure people in. The lack of clocks and the suppression of natural light, so that everyone lost track of time. The careful variation in ceiling heights, lighting levels and music zones to trigger different emotional responses. The strategic location of the bathrooms, to minimise time off the floor. The purposefully labyrinthine layout, so that the sightlines provided neither a glimpse of a possible way out, nor allowed a potentially overwhelming view of the entire space. In this broad church, you were damned from the moment you walked through the door.

There. A man with his back to him at the neighbouring blackjack table, his head snapping back a little too fast to suggest the glance he had just given him had been accidental. And again, only this time he didn’t break eye contact. He knew Tom had seen him. He was tipping the dealer, getting up. This was it.

‘Blackjack table,’ Tom muttered into his mike, hoping the others could hear him over the noise. ‘White hair, black…’ His voice tailed off as the man turned round and nodded.

Dressed in a black suit, he was about five feet ten with a curling mop of white hair and a farmer’s sun-blushed cheeks that echoed the red handkerchief peeking out of a trouser pocket. But it was the white band encircling his neck that had drawn Tom’s attention, its unexpected glare seeming to cast a bleaching wash over everything at the periphery of his vision.

‘He’s a priest,’ Tom breathed in disbelief, as much to himself as anyone.

The man advanced towards him, Tom reassured that as Jennifer had predicted to Kezman earlier, he wasn’t carrying anything that might have contained the painting. That would have marked him and whoever he was working for as amateurs, and amateurs were unpredictable and more easily spooked. Instead, slung over his left shoulder was a tired leather satchel.

They met in the middle of the main aisle. Saying nothing, the priest reached into his bag and handed Tom a series of photographs. They showed the Nativity, but in more detail this time, with closeups of the faces and hands, always the hardest things to paint. From what Tom could tell, the brushwork looked genuine, and although the canvas had been slightly damaged over the years, overall the condition was very good, the faint reflection of a camera flash in a couple of the photos suggesting that it was being kept behind glass.

There was no sign of a signature, but Tom took that as further proof of the painting’s probable authenticity. As far as he knew, Caravaggio had only ever signed one painting, The Beheading of the Baptist, where he had marked an M for Merisi, his family name, in the blood spilling from John the Baptist’s neck.

‘Is it close?’ Tom asked.

‘Close enough,’ the priest replied, Tom detecting an Italian accent.

‘I need to see it.’

‘Is that the money?’

‘Twenty million dollars,’ he confirmed, tapping the case nearest to him with his foot. ‘Unmarked, non-sequential bills, as requested.’

‘Bene, bene.’ The priest nodded. ‘Good.’ There was an anxious edge to the man’s voice that surprised Tom. For a pro he seemed a little tense, although twenty million was enough to make most people tighten up.

‘I need to see the painting first,’ Tom reminded him.

‘Of course,’ the priest said. ‘You have a car?’

‘The painting’s not here?’

‘It’s not far. Where’s your car?’

‘The money’s going nowhere until I see the painting,’ Tom warned him.

‘Don’t worry,’ the priest immediately reassured him. ‘We have a deal, see -’ He reached for Tom’s hand and shook it energetically. ‘You have the money, I have the painting, we have a deal, yes?’