Almost immediately he jumped back, the stairwell thundering with the sound of heavy footsteps and urgent shouts that he knew instinctively were heading towards him. He glanced around, looking for somewhere to hide and realising that he had only moments to find it. But before he could move, he felt a heavy hand grip his shoulder. He spun round. It was Ortiz, his chest heaving, eyes staring.

‘This way,’ he wheezed, urging him towards an open office. ‘Quickly.’

Tom hesitated for a fraction of a second, but the lack of a better option quickly made up his mind for him. Following him inside, Tom watched as Ortiz shut the door behind him and let the blinds drop with a fizz of nylon through his fingers.

‘Can you really find them?’ he panted, peering through a narrow crack as a group of armed men, led by Stokes, charged past them towards Jennifer’s office.

‘What?’ Tom asked, not sure he’d heard right.

‘Jennifer’s killers? Can you find them?’ Ortiz repeated, spinning round to face him, his face glistening, the half-hidden tattoo on his neck pulsing as if it was alive.

‘I can find them.’ Tom nodded. ‘If I can get out of here, I can find them.’

Ortiz stared at him unblinkingly, as if trying to look for the trap that might be lurking behind Tom’s eyes.

‘Where are you going to go?’

‘It’s probably better you don’t know.’

‘What will you do?’

‘Whatever I have to,’ Tom reassured him in a cold voice. ‘What you can’t. What Jennifer deserves.’

Ortiz nodded slowly and gave a deep sigh, Tom’s words seeming to calm him.

‘Good.’ He stepped forward and pressed his card into Tom’s hand, pulling him closer until their faces were only inches apart. ‘Just call me when it’s done.’

Releasing his grip, Ortiz reached out and with a jerk of his wrist, flicked the fire alarm switch. The siren’s shrill cry split the air.

‘Go,’ he muttered, his eyes dropping to the floor. ‘Get outside with everyone else before I change my mind.’

With a nod, Tom sprinted back towards the stairwell, the siren bouncing deliriously off the walls. Taking the steps two at a time, he raced down towards the ground floor, doors above and below him crashing open as people streamed on to the staircase, their excited voices suggesting that they knew this wasn’t a drill.

As he cleared the first-floor landing, however, he was forced to slow to a walk, the crowd backing up ahead of him. Peering over their heads, he saw that a line of security guards was quickly checking everyone’s ID before allowing them to leave the building. Had Stokes tipped them off, guessing that he might be using the alarm as cover? Either way, Tom had to do something and do something quickly, before the tide of people behind him swept him into the guards’ waiting arms.

Waiting until he was almost at the bottom of the penultimate flight of stairs, Tom deliberately tripped the man ahead of him and, with a sharp shove, sent him crashing into the wall opposite. He smacked into it with a sickening crunch, a deep gash opening up in his forehead, the blood streaming down his face.

‘Let me through,’ Tom called, hauling the dazed man to his feet and throwing his arm around his shoulder. ‘Let me through.’

‘Get out the way,’ somebody above him called.

‘Get back,’ someone else echoed. ‘Man down.’

Seeing Tom staggering towards them, one of the guards stepped forward and supported the injured man on the other side. Together they lifted him along the narrow path that had miraculously opened through the middle of the crowd, people grimacing in sympathy at the unnatural angle of the man’s nose.

‘He needs a doctor,’ Tom called urgently. ‘He’s losing a lot of blood.’

‘This way, sir.’

The line of guards parted to let them through, another officer escorting them clear as he radioed for a medic. Reaching a safe distance, they sat the still groggy man down on the sidewalk, an ambulance announcing its arrival moments later by unnecessarily laying down three feet of rubber as it stopped. The paramedics jumped out, threw a foil blanket around the man’s shoulders and pressed a wet compress against his nose to stem the flow. Tom stepped back, leaving the two guards to crowd round with words of advice and encouragement. Then, seeing that no one was watching, he turned and walked away.

Standing at a seventh-storey window, FBI Director Green watched Tom disappear down D Street with a smile. Smartly dressed with a crisp parting in his brown hair, plump cheeks and perfectly capped teeth, he was engaged in a running battle with his weight, the various scarred notches on his belt showing the yo-yo fluctuations of his waistline.

He knew Kirk well enough to guess that he’d find a way out of that room and that, when he did, he’d head straight for Browne’s safe. That’s why he’d ordered her swipe card not to be cancelled. That’s why he’d briefed the operator to let him know if anyone called asking for directions to her office.

The truth was that Kirk was her best chance now. While the Bureau was holding its collective dick worrying about who was going to get blamed for one of its most promising young agents getting killed, Kirk would be out there making things happen. Browne had trusted Kirk with her life many times before now. It seemed only right to trust him with her death too.

Viale XXI Aprile, Rome 18th March-4.51 p.m.

Panting, Allegra sprinted on to the Via Gaetano Moroni and then right on to Via Luigi Pigorini, the cars here parked with typical Roman indifference -some up on the kerb, others end-on to fit into an impossibly narrow gap.

Gallo…a killer? It made no sense. It was impossible. But how could she ignore what she’d seen? The shots fired from the doorway; Gambetta staggering backwards and toppling to the floor like a felled tree; Gallo’s animal grunt as he had hauled the carcass across the concrete; his stony face and cold eyes.

She found her stride, her ragged breathing slowly falling into a more comfortable rhythm, her thoughts settling.

Had Gallo seen her face? She wasn’t sure. Either way, it wouldn’t take him long to pull the security footage. The only thing that mattered now was getting as far away from him as she could.

Seeing a taxi, she flagged it down and settled with relief into the back seat as she gave him her home address up on the Aventine Hill.

Whether Gallo had seen her or not, at least his motives seemed pretty clear. He’d killed Gambetta so that he couldn’t tell anyone else about his discovery of the links between the murders. Why else would he have paused under the faltering neon light where Gambetta had taken Cavalli’s evidence box down from its shelf. He’d been looking for the lead disc, so that no one else would think or know to make the connection. No one apart from her.

‘What number?’ the driver called back over his shoulder ten minutes later as they drew on to the Via Guerrieri.

‘Drive to the end,’ she ordered.

With a shrug, he accelerated down the street, tyres drumming on the cobbles as Allegra sank low into her seat and peered cautiously over the edge of the window sill.

There. About fifty yards past the entrance to her apartment. A dark blue Alfa with two men sat in the front, their mirrors set at an unnatural angle so they could see back up the street behind them. She didn’t recognise the driver as they flashed past, but the passenger…the passenger, she realised with a sinking heart, was Salvatore. Not only had Gallo clearly seen her, but he had already unleashed his men on to her trail.

‘Keep going,’ she called, keeping her head down. ‘I’ve changed my mind. Take me to…Take me to the Via Galvani,’ she ordered, settling on the only other place she could think of. ‘It’s off the Via Marmorata.’

Making a face, the driver mumbled something about women and directions, only to roll his eyes when they reached the Via Galvani ten minutes later and she again asked him to drive down it without stopping.