David checked his watch; there was just enough time. He removed his rucksack and placed it on the ground a few feet from the car. He opened the back passenger door and made sure the child lock was activated. He then grabbed the heavy steering wheel lock from the passenger footwell and moved round to the boot of the car. He listened for a moment, braced himself with the steering wheel lock, and then opened the boot.

The stench was worse in the clean air of the quarry, and the putrid smell rose up, hitting him in the face. Both bodies were still. He leant in to pull Erika out, but her arm shot out and she caught him on the side of his head with a wrench.

He staggered back for a moment, seeing stars, but as she started to climb from the boot, he swung the steering lock round and hit her in the side of her left knee. She collapsed onto the ground, groaning. He did the same to her right knee. She cried out again. David grabbed her and dragged her round to the rear passenger seat.

‘Don’t fight me,’ he said.

‘David. It doesn’t have to end like this,’ gasped Erika through the pain, seeing the vast expanse of water stretching out below them. She couldn’t move her legs, and one of her arms was dead from being pinned under her in the car. Her head was still woozy where she had been hit, and she was fighting to think. Her head struck the doorframe as David hauled her body into the car. The door slammed and she looked around, seeing she was in the back, sitting behind the driver’s seat. She caught sight of her face in the mirror. Her blonde hair was slick with blood on one side, and plastered against her scalp. One eye was so blackened and swollen that it was closed. She tried the door beside her, but it wouldn’t open. She leaned across, groaning in agony, and tried the other passenger door. It, too, wouldn’t open.

The front passenger door opened, sucking out the air, which was replaced by the stench of death. David was carrying the body of the dead girl, looking more horrific than Erika had imagined. The girl had long dark hair, but her face was swollen with two black eyes and multiple cuts. Strands of hair had been pulled out from the side of her head. Erika looked down and saw strands of the girl’s hair stuck to her own jacket.

David shoved the girl into the front passenger seat, and her head flopped to one side. Erika could see that her eyes were a pearly blur, and her tongue had swollen, oozing from her mouth like a huge, purple-black slug.

‘David, listen. I don’t know what you’re planning, but you won’t get away with it . . . If you surrender now, I can . . .’

‘You really are an arrogant bitch, aren’t you?’ he said, peering through the seats. ‘Here you are with the shit beaten out of you, stuck inside a car in the middle of nowhere, and you think I’m going to surrender to you.’

‘David!’

He leant over and punched her hard in the face. Her head jerked back and bounced off the window. Blackness flooded her vision for a moment. When she came to, she felt a seatbelt being pulled around her and fastened with a click. The door beside her slammed shut. David peered through the seats, taking off the handbrake. She felt the wheels jerk free.

‘It looks like it’s going to freeze again tonight,’ he said. The driver’s door slammed, and seconds later the car began to roll forward, towards the edge of the quarry.

The car quickly picked up speed. David broke into a run, still pushing. He pulled back a few metres from the edge, and the car surged forward and vanished over the edge.

Erika felt the wheels leave the edge of the quarry. The horizon seemed to fly upwards, and was replaced by bright blue, hurtling towards the windscreen. David had strapped both her and the dead girl in, but the whiplash from the impact was excruciating nevertheless. The car was submerged in bright blue for a moment, and then righted itself and broke the surface, the interior blazing with natural light. Erika searched frantically for the seat belt clasp, but it wouldn’t open. The windows had been left open a few inches, and ice-cold water was surging inside, rapidly filling the car. Erika had expected to have time to react; she tried to open the door but the child lock was still activated. Water flooded in the windows, and within seconds the freezing water rose to her chest. Panicking, Erika grabbed as deep a breath as she could, and the roaring sound from above ceased as she was submerged. The car began to sink at a terrifying rate, down, deeper and darker. The weight of the engine sent them into a head-on collision with the bottom of the quarry.

The police helicopter reached the edge of the quarry as, far below, they saw David’s car roll over the edge and hit the water. Moss and Peterson were in the helicopter with a police pilot. They had an open radio link to the incident room in Lewisham Row, and backup vehicles and an ambulance were on their way.