The newcomer surveyed the scene. The young man’s eyes were still open, still seeing; his limbs, however, were completely paralysed. The injection had done its work. It was a useful compound, suxamethonium chloride – a muscle relaxant that had the effect of completely paralysing the body while leaving the mind aware and remaining difficult to detect in the bloodstream. He did not have the opportunity to use it often, but for this particular job it was just right.

He opened his briefcase, dropped the syringe inside and then put his gloves back on. Walking into the kitchen he searched through the drawers, taking good care to put everything back in its proper place. He grunted with contentment when he found a roll of large, clear polythene bags. He’d brought some with him, of course, but much better for his purposes to use what was already here. He tore off a bag – it shimmied a little under the soft touch of his gloves – left the roll artfully on the cluttered work surface, then returned to the main room.

It was not entirely straightforward to remove the young man’s clothes, but he managed it and dumped them in a pile by the coffee table. Returning to his naked body, he slipped the plastic bag over his victim’s head. He pinched the open end around his neck before inclining his head slightly and looking directly into the young man’s eyes.

It was very hard to read any expression there, but his victim would know he was being suffocated. It was curious to witness the young man making no attempt to struggle. The plastic bag formed a concave hollow around his mouth which popped out and then in again. Over a period of about a minute the movement became gradually weaker until it stopped completely.

The young man was dead, but his assassin’s work wasn’t finished. Not yet. Letting go of the plastic bag his eyes fell upon another door at the opposite side of the room. He went through it to find the young man’s bedroom. It was stark: a chest of drawers, a cupboard and a large, unmade bed in the middle; an iPod left carelessly on the floor and a laptop computer next to it. The man took the laptop and switched it on. Opening the Internet browser he searched through the history of recently visited websites. They were largely what he expected: links to details of fast cars and gadgets, information on handguns and other weaponry, military websites and of course a good deal of pornography. He smiled. It looked like he wouldn’t be needing those magazines after all. Using the wireless connection that the laptop had automatically picked up he navigated to what looked like the young man’s favourite – it was nothing too specialist, he noted as he started to play a long video. He did, however, allow himself a few guilty seconds to watch the three naked, entwined bodies before placing the laptop on the coffee table.

Only then did he step back to admire his handiwork. It pleased him.

Auto-erotic asphyxiation. The young man had a history of it. For a moment the fat man wondered what pleasure anyone could possibly derive from the act of bringing oneself almost to the point of suffocation in order to achieve sexual gratification. Then he shrugged. People such as the young man he had just killed derived pleasure from all manner of pursuits that he himself would never consider. Foolish pursuits. Dangerous pursuits. In a strange kind of way it made them easier to eliminate. No doubt some girlfriend from the past would be found to confirm the young man’s penchant for such activities. He felt confident, from his considerable experience of these things, that his death would be put down to a tragic – if unsavoury – accident.

It wouldn’t do to stay here much longer. The man closed up his briefcase, glanced momentarily and with satisfaction at his little production, then let himself out of the flat. He closed the door silently before ascending the stairs, turning right and walking calmly back to the Uxbridge Road.

This really was quite the most unpleasant part of London, he decided. He would be very glad to get back home.

Much like the portly man who even now was making his way back up the Uxbridge Road, the car that travelled round the raised, curved slip road and into an almost diametrically opposite part of London was not built for speed. But it was being driven very quickly anyway.

It was a Renault, small and neat. The interior was immaculately tidy and faintly perfumed. It would be easy to mistake this car for one that had just been driven out of the showroom, but in fact it was a couple of years old. It just happened to have been very well looked after. The owner, Kelly Larkin, sat in the passenger seat. Her hair, which she had spent so much time on that morning, was mussed and unruly – at least by her standards. The scream of the small engine roared in her ears and, not for the first time, she found herself shouting. ‘For God’s sake, Jamie! Just slow down!’

No more than fifteen metres ahead, a car heading towards them moved into their lane to avoid a parked motorbike. Kelly clamped her eyes shut as her boyfriend slammed the engine into fifth gear and swerved sharply to avoid it. The angry sound of a horn filled her ears before fading quickly away. When she dared to open her eyes again the car had completely left the motorway and was on a wide, three-laned thoroughfare that would take them past Walthamstow and into that unfashionable slab of north-east London where she lived.

Jamie had a grin on his face. He was a good-looking guy, there was no doubt about that, but at the moment he looked like a psycho. He chewed on an imaginary piece of gum and held the steering wheel with a single finger. When he glanced into the rear-view mirror it was to admire himself.

At twenty-six, Jamie Spillane dressed like a teenager in his Converse boots and hooded tops. Kelly found herself with him quite against her better judgement; but at her age, thirty-three, she found herself being less and less picky in her desire not to end up on the shelf. She glanced at the speedometer. Ninety-six. ‘Please, Jamie,’ she begged as her left hand clutched the passenger door even more tightly. Perhaps pleading would have a better effect than shouting. ‘Please just slow down.’

Jamie turned to look at her. Instantly she wished she’d kept her mouth shut, because it meant his eyes were off the road. He had a neatly shaved goatee beard, which actually made him appear almost childlike because it looked so inappropriate. It was that look that had first attracted her to him, but right now she wished he would just grow up. He winked at her. Either he was totally oblivious to her fear, or it thrilled him. Whatever, he didn’t slow down. Kelly just closed her eyes again and tried to master the cold sickness that left her body weak. She would have liked to start crying, but somehow she was too scared even for that.

As they entered the outskirts of Walthamstow, Jamie reduced his speed. Not by much, though. He ran two red lights – they were just the ones Kelly counted when her eyes were open – and as he turned into the top of Acacia Street the speedometer was still wobbling around fifty. The tyres screeched as he took the corner; Kelly screamed at the sight of a couple of kids running across the road ahead. But at the last minute he swerved again and by some act of God managed to miss them. Outside her flat he swung the car to the side of the road. One tyre pulled up on to the kerb as he came to a halt, but he didn’t bother to rectify his inexact parking. He flamboyantly turned off the ignition, flung his arm into the air and turned once more to look at Kelly. His grin was still there and he was out of breath, as though he had run all the way from the M11, rather than driven.

Kelly opened the car door and stormed out. The air was cold, but she was too furious to take her coat from the back seat. As her heels clattered along the pavement she found that her mind was bubbling with angry words. Kelly was not the type to have a stand-up argument in the street, but, knowing that if she stopped now she wouldn’t have much choice, she hurried to her front door. If Jamie thought he was coming in after that little display, he had another think coming.