He shone his torch around, trying to get a better sense of what they’d uncovered. At first he thought the floor was covered in sharp rocks, but he peered closer, trying to pin down the irregular shapes of those stones. They certainly weren’t man-made, but they weren’t typical stones, either . . .

He backed away with a yelp through his regulator, dropping his torch and sending frantic shadows jumping all over the ceiling. He bumped into Ahab, who gripped Forest’s arm to help him find his balance.

The floor of the cave was completely covered in bones.

Forest had a sickening sense of déjà vu, as though they were back in Alexandra and Huck’s tomb.

Ahab gave his arm a comforting squeeze.

Why is he so calm?

Ahab reached into a nearby pile and pulled out a small flat object. He touched his bare thumb to the sharp edge and it came away with a prick of blood. He swept his torchlight around the area while Forest slowly eased back into the water. All those bones, the toxic air, the blood on Ahab’s finger . . .

He let the water support him, already feeling better. Ahab, without straying far from the pool of water that was their exit from this death trap – moving expertly even in his fins – scanned through some more of the debris.

When the old man returned, Forest went first, swimming back through the tunnel, eyes straight ahead, then straight up to the boat.

He gasped for breath once he was out of the sea, clambering up onto the boat and taking in the cool fresh ocean air. He’d never take that for granted again. He felt like vomiting.

All that, and not even a hint of treasure. He could barely begin thinking about what happened next, but that cave had not been what he’d been hoping for. What he needed it to be. Not even close.

Ahab was not far behind. Once he was on deck he took his mask off and pulled that flat round stone out of his diving pouch. His beard was dripping wet, his eyes shining as he held the stone up to the light as though it were made of gold.

‘It’s another tomb,’ said Forest.

‘They weren’t human bones, son.’

He put the stone carefully back into his pouch.

‘What’s so special about a bunch of bones and rocks?’ asked Forest. ‘That’s not treasure!’

‘We need to get back to the Mermaid’s Darling, son,’ he said, distracted. ‘Hold on to something.’

CHAPTER 47

MACKENZIE

Mackenzie stood at the prow of the old houseboat, the MV Anne, watching the wide blue waters of Fortescue Bay, which reached out from the mouth of the tidal river where they were moored. The bay was cupped between giant sea cliffs that levelled out to the flatlands of the peninsula.