He stopped in front of me, then turned slightly towards the front window as something caught his attention.

I could hear it too. The angry whirr of a helicopter overhead. I felt a surge of elation.

It disappeared as he turned back to me and raised the gun. 'Sorry I can't linger a while, Mr Fallon, but I have business to attend to. Goodbye.'

I thought of Yvonne. I thought of Chloe. I thanked God they were safe. I wished I could have seen them again.

'Fuck you,' I hissed, just before he pulled the trigger.

Fifty-eight

Wanstead, in east London, is an attractive middle-class enclave with a village-like feel, and the road where Dominic Moynihan lived was a leafy stretch of expensive-looking Edwardian townhouses, which had now been sealed off at both ends by police vehicles with flashing lights. As they pulled up, Bolt spotted the blue Mazda parked further along, already surrounded by scene-of-crime tape.

He and Mo Khan showed their IDs and made their way through to an inner cordon of patrol cars and riot vans which had been positioned in a rough semi-circle in front of one of the houses. Several dozen officers – a mixture of Territorial Support and plainclothes – milled around without much urgency, while a handful of officers from Scotland Yard's elite armed unit, CO19, were positioned behind the cordon with their weapons facing the house.

As they approached, one of the plainclothes officers – a youngish guy with wispy blond hair and a suit that looked too expensive for a police salary – peeled off from the throng to come and greet them. 'DCI Max Carter, Counter Terrorism Command,' he said decisively, putting out a hand, his accent unmistakably public school. 'I've got the unenviable task of being in charge on the ground here. Are you the SOCA guys?'

'That's us,' said Bolt.

'I've only just got here myself,' continued Carter, 'but we've had officers on the scene for twenty-five minutes now.'

'Is anything happening in there?' asked Mo.

Carter shook his head. 'I don't know. We've tried to contact them by phone but the landline's not being picked up. We've also been using the loudhailer, but to no effect. Do either of you know the person who lives here?'

'We don't,' said Bolt, 'but we believe we know the identity of someone who's in there at the moment. A Mr Robert Fallon. He's the person who broke this whole thing. It's possible that someone came here to kill him driving the blue Mazda we were tracking.'

'Didn't he have a police guard?' asked Carter, sounding surprised.

'We didn't believe he was any longer in danger,' Mo replied quickly.

'Oh.' He raised his eyebrows. 'Well, the Mazda's still here, so we have to assume that the driver is too. I've got more officers round the back so if he is, he's not getting out.'

Bolt hoped that this was the case, and that the driver was holding Fallon and possibly his friend Moynihan hostage in there, but the fact that there'd been no signs of activity suggested otherwise. 'There's only one way to find out,' he said. 'We need to go in. And if he's there, we need to apprehend him alive, because he'll almost certainly know the location of the lorry with the gas.'

'As I'm sure you'll appreciate, Agent Bolt, I'm reluctant to storm the place until I've exhausted all other options. Because of the risk of casualties.'

Bolt could understand his position. One of the problems with modern British policing was the fact that everything had to be done so completely by the book that it resulted in a culture of risk-averseness that harmed the force's effectiveness.

But the lorry and its deadly contents made this situation very different.

'You know about this gas, Max,' said Bolt quietly. 'It could be anywhere. It could be en route here for all we know, primed and ready to blow.' He remembered that Mo's family lived only five miles away, and though his colleague's face remained impassive, he moved on quickly. 'If you need to get authorization, get it now. If you need me to speak to DAC Bridges, that's fine too. But either way, I'm going in.'

There was a huge crash as the Enforcer – the heavy steel cylinder used by the UK police for fast entry – was slammed against the main lock on Dominic Moynihan's front door by an immense TSG officer in full riot gear.

The door flew open, the TSG guy got out of the way, and then there was a cacophony of cries of 'Armed police!' as the first CO19 officers stormed inside.

'Clear!' came a shout, and then they were all pouring in, close to a dozen in number, kicking open doors on the ground floor, moving up the stairs, rapidly securing the area.

'Let's go,' said Bolt, and the next second he and Mo were running out from behind the cordon, across the short stretch of tarmac, and into the house itself through the open front door.

The hallway was empty. There were doors on either side of it, both of which were open, and a wooden staircase immediately ahead. Bolt could hear plenty of banging about on the next floor up, but no sound of resistance.

'Clear!' someone shouted from one of the upstairs rooms.

To Bolt's left was a spacious modern kitchen, to his right was a living room. There were voices coming from inside, but there was no urgency in their tones.

He pushed his way in, with Mo following, and the first thing he saw was the body of a dark-haired man in his early thirties lying on his back between an expensive-looking sofa and a bookcase. He'd been shot in the face, and there was a pool of blood staining the cream carpet a deep burgundy colour. This must have been Dominic Moynihan, and it was obvious that he was dead.

Two CO19 officers, MP5 machine pistols now down at their sides, stood next to an identical sofa on the other side of the room. As Bolt came further inside he could see they were looking down at another body only the legs of which were visible, and that one of them was holding an arm, feeling for a pulse.

'No, he's gone too,' said the officer, releasing the arm.

Bolt swallowed and walked towards them. As they moved aside, he saw who it was lying sprawled on his back, and groaned. 'Fuck.' He spoke the word louder than he'd intended.

'It's not your fault, boss,' said Mo as they looked down at the corpse of Rob Fallon.

He'd been shot in the centre of the forehead by someone with a good aim, the blackened entry wound perfectly placed. He also had extensive facial bruising and an injury to his temple that had left him with heavy bloodstains down one side. Just seventeen hours ago he'd been sat up in a hospital bed talking to them, seemingly safe from those who wished to kill him. And now they'd finally managed it. Beaten him savagely, then casually destroyed him. Bolt knew who'd done it too.

But Hook was nowhere to be seen. As usual, he was one step ahead of everyone.

'It is my fault, Mo,' he said quietly. 'I should have kept him under guard until all this was over.'

'You weren't to know. None of us were. I mean, there was no logical reason to kill him, was there? What possible threat could he have been to them now?'

Bolt sighed. He couldn't understand why Hook would have done it either. Even for a cold-blooded killer like him, to commit another double murder on the day he took delivery of the gas seemed unduly risky.

As more officers entered the lounge, including a shocked-looking DCI Carter, Bolt turned away from the body. There was no point staying. This was a crime scene now and his presence was just cluttering the place.

'Is he dead as well?' asked Carter.

Bolt nodded, and walked past him into the hallway.

'What now, boss?' asked Mo.

'God knows,' said Bolt, looking at a framed A4-sized photo on the wall of a group of men in dinner suits grinning at the camera. There were three of them in all, and he recognized the one on the left as the other dead man in the living room. Dominic Moynihan was holding a champagne bottle in one hand and a half-full glass in the other. He was a good-looking guy with a confident demeanour, and he seemed to be without a care in the world. Bolt hated the way that death so effectively snatched all that away from a person, leaving just a hollow husk behind. Now, he and Rob Fallon were just dead bodies – two more to add to the growing tally. He wondered if the next one he was going to see would be Tina Boyd, the woman who'd never quite been his lover.