The tunnel started to glow, the orange light so bright they had to shield their eyes. But still they pressed on. They rounded a final corner – and there it was. A burning orange ball that could only be the Earth’s core.

But there was no sign of Thanatos.

‘Where is he?’ said Virgo. ‘Are we too late? Perhaps we should . . .’

The rest of her suggestion was lost as a blow to the back of her head sent her crumpling to the ground.

‘Virgo!’ Elliot yelled, running to her.

‘You two just never learn,’ said Thanatos, stepping out of the shadows. ‘And I am seriously tiring of your constant interference.’

He lifted his fist to administer a similar blow to Elliot. But, once again, the Daemon was repelled by the invisible force that had kept Elliot safe ever since he freed Thanatos from Stonehenge.

‘How irksome,’ he sighed. ‘Well, now. There’s more than one way to skin a cat. Remember this?’

Holding the Chaos Stone above his head, Thanatos roared a sharp command.

‘Earth Stone! Drop!’ And the diamond shimmer of the Earth Stone began to glow.

Elliot looked up at the ceiling. He knew what was coming. He’d used the same trick once before.

The stalactites started to tremble above him, quaking with the power of the Earth Stone. Elliot squatted down and shielded his head as the stalactites fell to the ground, imprisoning him in a stone prison right in front of the Earth’s core.

‘Now. It’s worth pointing out at this juncture,’ Thanatos drawled, ‘that I delivered on my side of the bargain. I kept my oath. I gave you your mother back. If you chose to lose her again, I’m afraid that’s your business.’

Elliot felt a wave of emotion rise up through him. But it wasn’t sadness. It was courage. That’s why he let his mum go. He hadn’t lost her. She was with him every step of the way. He knew that now.

‘So, I’m freed from my oath on the Styx,’ said Thanatos. ‘Now I can do whatever I want. And I want to kill you, Elliot Hooper. Can’t lie – always have.’

Elliot stared the Daemon straight in the eye. He wasn’t going to show Thanatos his fear. He was sick of being afraid. If this was the end, he was facing it head on.

‘Get stuffed,’ he said.

‘Oh, for shame,’ sighed Thanatos. ‘You’ve had all this time to think of the best thing to say when I kill you, and that’s the best you can come up with? Oh, well, it will have to suffice. I have other things to be getting on with.’

The Daemon turned, stepped over Virgo’s unconscious body, and held the Chaos Stone aloft, filling the dark void with its ethereal glow.