He gripped Sophie’s arms. ‘Call me jumpy, but I reckon we need to reach our destination by nightfall or something bad’s going to happen.’

‘Any particular reason?’

‘A gut feeling.’ Increasingly, he found that his instincts were rarely wrong, as though he was becoming more sensitive to subtle warning signs.

Sophie nodded and picked up her speed.

As the darkness washed in from the east, gloom rose up around the trunks of the trees and the sounds of the hillside became eerily magnified. Every windborne rustle became a predator at their backs, every footstep the thunderous beat of a buried heart.

Fifty yards ahead, the energy flows congregated just below the lip of the hill’s flat summit. As night fell, they began to run. In that same instant, a whispering rose up from the trees, echoing across the deserted hillside. They couldn’t make out the words, but there was something in the sound that made them feel sluggish and gloomy. They slowed to a walk, then stopped and looked around for the source.

‘What is that?’ Mallory asked.

‘I can feel it in my head,’ Sophie said. She swayed, mesmerised and suddenly overcome by melancholy.

Mallory grabbed her and forced her to look at him. ‘Don’t listen.’ He propelled her onwards as fast as she would go, scrambling over humps, tumbling through nettles, stinging and winding themselves. The unsettling whispering continued, unmistakably growing closer.

‘It’s hunting us,’ Sophie gasped. ‘What is it?’

‘Just concentrate on running.’ Mallory’s eyes darted around the hillside, but it was impossible to see clearly in the gloom.

They emerged from the trees and bushes on to a grassy slope where they had a clear view of a surging and spitting whirlpool of Blue Fire ahead.