He shook his head and clutched at the walls to orientate himself again, feeling the handle of the pump tangle in his legs until he kicked away. The cold was already creeping into his bones and turning his fingers and toes numb. He didn’t have very long to do this. It had to be now, or never.

Cooper’s head went under again, and then he was in the doorway, pushing against the wooden frame. It was too dark to see anything in front of him. But he could hear David Headon’s voice in his head, telling him that the monitoring room was only sixteen feet long. He remembered thinking that it was a small space for three men to spend so many hours in. Seven feet wide and sixteen feet long, like a giant coffin. He could reach the end of it in two strokes.

His violent movements stirred up silt and debris from the concrete floor. Floating objects bumped against him as he kicked forward, like invisible creatures swimming around him in the black water. A plastic bucket, a jerry can that spun away when he cracked his elbow against it. And something rough and fibrous that flapped slowly towards the floor.

Then a long, loosely jointed shape swung into his face. A familiar shape. A human arm. His lungs aching, Cooper grabbed at a sleeve and began to kick backwards towards the door. For a long second, he felt something holding him down, the door getting in his way as he confused the direction of the ladder. In a gleam of light from above, he saw a white face turning slowly towards him, a floating blank-eyed face, staring and staring.

Then his foot found the grille at the base of the shaft, and a rung of the ladder, and he was finally pushing upwards to the light. As he gulped air, he felt hands reach down towards him. Someone had lowered a rope. Voices came down from the sky that he almost couldn’t make out.

‘Is he dead?’

‘Are you all right?’

But he didn’t know the answer to either question.

Chapter Forty-two

Tuesday

JULIANA VAN DOON hovered over the body of Michael Clay, laid out on the mortuary table in Edendale. The body exuded an almost palpable aura of cold, the blue tinge to his skin strange and alien in the mortuary lights.

‘No, he didn’t drown,’ she said. ‘There was no water in his lungs. But he suffocated all the same.’

Fry shivered involuntarily. A visit to the mortuary wasn’t her idea of the best way to start the day. But today it seemed somehow appropriate.

‘Suffocated?’ she said. ‘How can that be?’

‘Oxygen deprivation.’

Tensing, Fry waited for the patronizing remark, but it didn’t come. Instead, the pathologist looked down at the body, and wouldn’t even meet her eye. Mrs van Doon seemed awkward with her this morning, almost as if she’d heard something that had changed her attitude. Fry told herself she must be imagining things. Yet still the pathologist looked away as she continued to explain.