‘What?’ said Huck. ‘Find a home? I’ll come live with you in a drug lord’s mansion? Don’t you get it – you and me, we don’t get to have happy endings.’

‘I’m going back there,’ said Forest. ‘I’m finding that treasure and I’m clearing your name.’ He looked down at the waves, gauging that the tide was heading out. No time like the present. ‘I’ll save you, whether you want it or not.’

He left before Huck could stop him.

Fog had come in from the sea by the time Forest reached the boulder field. He stood at the entrance to the cave, shivering in the sea breeze, the fog adding to the sense of menace. A tomb, that’s what Huck had called it.

He climbed inside. Dead silence. No plants, no lichen or moss, no bugs. Only dirt and dolerite, the cold of the earth and water, his shaky breath and his dancing torch.

He found a rock he could use to mark the walls, deciding it would be unwise to not leave a path to follow out. But though the twisting passages promised labyrinth twists, there were no dead ends. The inside of the cave was more like a sponge than a maze.

But with that first step, panic flooded him. He couldn’t do this, he was going to suffocate, he was going to drown . . .

He forced himself to think of Huck. He forced himself to think about what his friend had endured.

He took a deep, calming breath and continued on.

He went deeper, through the little corridors and the dank, dripping caverns, his torchlight sparkling off the walls. The further down he went, the wetter it became, with shells and seaweed gathering at his feet. That meant he had entered the tidal part of the cave. While he was confident it was low tide, he’d still need to proceed carefully.

He continued climbing even deeper, the heat long gone, replaced by damp cold, until his torch beam landed on the jagged entrance to another tunnel, the size of a fireplace. And there, at its lip, something square and flat and white. He approached it slowly, unsure if it was what he hoped it was, but, sure enough, it had writing on it.

This was Alexandra’s diving slate.

The words written on it in waterproof pencil were a panicked scrawl, but readable enough: JESSE DEMPSEY KILLED US BECAUSE OF THE BONE CAVE.

And underneath those words, a roughly sketched map of Pirates Bay. An X in the middle of the water and coordinates noted down beside it.

He’d found it. He committed it all to memory, in case he accidentally wiped it clean, then picked it up.