‘The skull,’ said Ahab. ‘It has a cleft palate. Forest didn’t have a cleft palate.’

Forest looked at him blankly, failing to comprehend what Ahab was trying to tell him – Ahab could barely believe it himself.

‘But another boy did,’ said Ahab. ‘Jonah’s boy. Huck Donnager.’

Forest went very still. He turned to look at the crack as though seeing all within it anew. ‘Huck?’ he whispered.

He pushed past Ahab and into the hole.

Ahab stuck his head back through, watching as Forest picked his way down the wall.

‘There hasn’t been a confirmed sighting of Huck or Jonah since Forest went missing,’ said Ahab. ‘I thought the boy was on the run with his crooked old man, but . . .’

When he reached the skull, Forest seemed loath to touch it. He took a gulp of air, then picked it off the floor.

‘It’s damp,’ he groaned, as sludge fell away from it.

Dry-retching, he clambered over and handed it up to Ahab.

It was a child’s skull, and he’d seen right: it had a cleft palate. Ahab shuddered himself as he cradled the skull, imagining Alexandra and Huck drowning in that cave. He could almost hear the memory of their screams.

He pulled out of the crack and a moment later Forest followed, face pale in the torchlight.

‘You’re sure it’s Huck?’ said Forest, shaking uncontrollably.

‘I’m sure . . .’ Ahab put the skull down on the ground. ‘Let’s get out of this place.’

‘You’re not gonna bring him with us?’ said Forest. He couldn’t take his eyes off the skull. ‘You’re sure it’s Huck?’

‘We’ll tell the police it’s here. They wouldn’t want it moved far, and I don’t know what the outside air will do to it.’ His voice echoed in the cave, sounding foreign to himself.

Forest didn’t seem to hear him. He had crouched beside the skull, arms folded to try and stop himself from shaking.

‘But why didn’t Huck escape? Why didn’t he climb out?’

‘Huck had a bone deformity and an intellectual disability. In a dark cave, once it started filling with water, I imagine he would’ve panicked . . . knowing Alexandra, she would have comforted him in those last moments . . .’

He closed his eyes, just for one breath, in memory of her. She had been the best of all of them.

‘Right. Time for the truth. Why were the two of them here? How did Alexandra fit through that crack, and why did they only have one set of scuba gear?’

‘You’re not going to like the answer,’ said Forest.

Ahab had had enough of games. ‘Out with it.’ His whisper hissed and echoed in the cave.

Forest sighed, took a deep breath. ‘It was Jesse. Jesse trapped them in there.’

‘Jesse? Are you sure?’ But even as he said it . . .