The girl seemed wholly preoccupied with the task in hand; I ventured closer still, keeping in the background of the dream so as not to attract attention. But the girl had seen me. Her gaze was strangely penetrating, and when I tried to shift my ephemeral Aspect, to make myself inconspicuous again, I found that I couldn’t. I was caught.

The little girl looked at me. ‘Who are you?’

‘No one. Nothing.’

‘That’s not true. I’ve seen you before. Won’t you tell me your name?’

She must be the dreamer, I told myself. But like myself, she was lucid; clearly able to exercise control over aspects of her dream – and that included Yours Truly, trapped on a little island of Dream that might at any moment vanish into ephemera as soon as my dreamer chose to awake . . .

Perhaps, despite my precautions, I thought, I hadn’t been quite wary enough. I’d relied too much on my camouflage, believing myself invulnerable. And now I was caught between realities, unable to shift, at the mercy of the dark intelligence I’d wooed for so long, and which, whatever else it was, was certainly not a little girl.

‘Who are you?’ I asked, to gain time.

‘Heidi,’ said the little girl. ‘Did you see my sandcastle?’

I looked beyond her down the beach. The sun was going down, and the light was suddenly ominous. In its glow, the sandcastle looked even larger than before, and all at once it occurred to me that it looked a lot like Asgard.

I looked a little closer. Yes: there was Odin’s hall; the walls; the turrets and bridges and towers and gates. There was my place; and Sigyn’s; Idun’s garden; Freyja’s boudoir; all painstakingly built in sand, with the Rainbow Bridge arching out from the parapet.

The tide had suddenly started to turn. The wind, so clean and fragrant a few moments before, now smelt of mud and seaweed. In the glow of the setting sun, the waves were crested with frills of blood.

Once more I tried to shift my ephemeral Aspect. I was getting a bad feeling about this dream; the bloody light; the turning tide; the Sky Citadel built in sand. But again I found that I could not shift. The dreamer’s will was stronger than mine.

I looked up at the sky. It was purple. The waves had reached the outer walls of the sandcastle. The bridge of sand fell almost at once; the battlements might hold longer.

‘This is the bit I always like best,’ said Heidi, in a bright voice. ‘Watching it fall. Don’t you agree? Watching as the sea takes it back, grain by grain, until there’s nothing left?’

Silently, I nodded. Whoever she was, she had a point.