For a second, all I could hear was our heavy breathing echoing around cave walls. The chamber we were in was big, judging by the sound of it. I heard Sam take a breath, like he was about to say something. To ask if I was all right or make some joke.

But the voice that slid out of the darkness wasn’t his. ‘You are very late indeed.’

I fought to keep my heart slow as I fumbled for the knot that attached me to Sam. My shaking fingers finally found it and I struggled to untie it. I needed at least to face whatever this was standing up.

‘I must say,’ the voice came again, echoing around the chamber unsettlingly as my fingers worked frantically, ‘your predecessors usually took the door.’

Finally the rope came apart. Sam rolled off me, his warmth and solidity disappeared, and suddenly I was alone in the dark. I fumbled for the matches in my pocket as I sat up.

I struck one, sending up a small flare of light against the total blackness. It was enough to see by. To see Sam, only a few feet away, slumped on the ground, exhausted from dragging me through stone. And, just beyond him, a man.

I stepped back instinctively, heart leaping in fear as the stranger smiled at us from the other side of the cave. I knew instantly even as he did that he wasn’t mortal. He was a Djinni. I’d summoned a whole host of immortals under the palace. I knew now how to recognise them. Their human shapes were too polished, too perfect, like they were made of burnished bronze instead of flesh. They somehow looked both ancient and young at the same time, like they’d seen a great deal but still forgotten to give their bodies the nicks and wear that made mortals look human. And this Djinni, his clothes were something out of another age, one so long gone it had been forgotten.

And then there were the burning red eyes, which had a slightly wild look in them. Like a quickly catching fire that might consume everything at any moment.

I held the match higher. Tight iron shackles were strapped around his arms and legs, darkened with age but strong all the same. And around him, there was a circle of iron to contain him. It looked identical to the ones where I’d trapped the Djinn under the palace. Like it had been made by the same hands.

‘Who are you?’ I asked. My voice sounded raspy and unsteady even to myself as it echoed around the chamber.

‘Who am I?’ he rasped back in an unkind imitation, making those burning red eyes go wide. And then they narrowed, fixing on me suspiciously. ‘Who are you that you come here without knowing me?’ I didn’t answer. There was something about him that made me not want to give him my name. I didn’t know what he might do with it. ‘And what is that?’ He nodded towards Sam, who was watching from one step behind me, like he was ready to bolt back through the wall at a moment’s notice. ‘He’s not one of ours.’ He sniffed as if he could suss Sam out. ‘He smells like damp earth. He’s a child made by our cowardly brethren in the green lands.’ He talked like the Holy Books, in ancient, labyrinthine language designed to ensnare the listener. ‘He doesn’t belong here. I don’t trust him.’

‘Always nice to be wanted,’ Sam muttered.

Silence descended. And lasted.

This Djinni, he wasn’t going to be any use to us if he was wary of Sam. He might talk to me though. I turned back towards my foreign friend, but I didn’t need to say anything. Sam started shaking his head as soon as he saw my expression in the flickering of the match. ‘No, I’m not leaving. You’ve lost your mind.’

‘Don’t you still owe me one for saving your life?’ I tried for lightness. Like the prospect of being imprisoned in this cavern with an immortal creature alone wasn’t terrifying.

‘Oh, sure, I see, because if I leave now, it would make us even. Since Jin will kill me if I come back through that wall without you, thus making you saving my life entirely moot.’ He ticked off the life or death count on his fingers like he was doing arithmetic.

I leaned in close to him, the match flickering close between us. ‘And other folks might die if we don’t get some help.’ The flame reached my fingers now, almost scalding them before I dropped the match quickly, extinguishing it on the cavern floor. ‘Sam,’ I said in the dark, fumbling for a new match. ‘Please.’

By the time I’d lit a new one, Sam looked resigned. ‘I’ll give you two measures of “Whistling Jenny”, and then I’m coming back for you.’

‘What’s a Jenny?’ I asked.

‘It’s not a … she’s … Never mind.’ He sounded frustrated, even though I wasn’t the one who was talking gibberish. ‘It’s a working song we use to measure time in the fields. There are ten measures of “Whistling Jenny” in an hour.’

‘Give me seven measures.’

‘Three,’ Sam haggled.

‘Five, and I agree not to tell Jin or Shazad about that time you tried to kiss me.’

‘Deal.’ Sam grabbed my hand, shaking it firmly. He picked up the lingering end of the rope that stretched back through solid stone all the way to the other side, where it was anchored by Jin. He quickly looped it around my waist, tying a hasty knot. ‘So I can find my way back to you.’ He grinned at me. But just before he let go, seriousness sank over him. ‘You’d better still be in one piece.’

And then he turned away, stepping out of the narrow pool of light cast by my match, keeping hold of the rope, and with one quick look back he was gone. And I was alone. Alone in the dark with a Djinni.