I help Iris to her feet and we start making our way towards the marble gateway that has materialised out of nowhere at the edge of the field. Surely, surely, after all the tests, this must be the way to Orbis. We've only taken a few steps, however, when we realise Sky isn't following us. We look back to see her standing where we started, watching us unhappily.

"What's the matter with you?" I snap. Iris squeezes my hand warningly, but I refuse to pay attention the the guilt deep within me when I see the hurt on Sky's face. Iris's face is still pale and I can feel her pulse in her wrist, slow and weak, although it's getting stronger by the second. I can't seem to get the picture of Sky pointing the wand at her out of my head, her eyes narrowed and cold. In that fleeting second, she looked just like she had when we first met her, when she used her magic against us without a shred of remorse.

It's hard to believe that was only a day ago. It feels like a million years have passed since I ran away from my father's castle. Maybe it was stupid of me, but I had really began to trust Sky. That new person; the kind, broken girl who had told us so many stories about herself, who had helped talk me back to reality when I couldn't handle the ghostly visions in my test... She had felt like a friend. I thought we were going to overcome the adversities together, all three of us.

The reminder that I was wrong curdles inside me.

"I can't see it," says Sky now. The glimmer of hope that had danced in her eyes before has been blown out. Her words are listless, monotonous. "I failed the test. I can't get through."

"Maybe if I-" began Iris.

"Magic won't work," says Sky miserably. "Not this time."

The guilt in me heightens. What is she going to do now? Is she trapped in this lonely, endless field forever? As far as I can tell, the way back to our old kingdom has closed too. We're stuck in some kind of purgatory between realms.

"Oh, for God's sake," I growl. "Hold on to Iris. Maybe we can pull you through with us."

Sky's eyes widen with surprise. She hesitates, then walks towards us and takes Iris's free hand. Then we walk towards the gateway together.

I reach out as we draw nearer, trying to pull the gates open, but my fingers close on empty air, and we walk straight through the gates as though they aren't there at all. We're surrounded momentarily by the blinding white dazzle of mist, just like the one we jumped through to get here in the first place. I prepare myself to fall down into the fog, but instead the mist clears and we're suddenly somewhere else.

We seem to be on the edge of a wood, but it would be impossible to mistake it for King Klaudius's kingdom. The bark of the trees is lined with sparkling silver, and the leaves shimmer golden in the sunlight. I look behind me and the view takes my breath away: we're standing at the top of an impossibly high hill, and sloping below us is a patchwork of villages and countryside; lakes, rivers, even palaces and castles. They stretch as far as the eye can see, and looming on the horizon I see mountains standing proudly, blue in the distance, a line of them curving round the kingdom like a wall defending a fort.

Orbis is even more incredible then I imagined.

"It's beautiful," Iris says softly beside me, turning around to see the view better. She lets go of my hand and stands up on her own, only ever so slightly unsteady. She's recovering quickly, and I wonder if it's anything to do with her newly gained magic. She looks back at the trees and points her finger at them, and a swirl of golden leaves are whisked from their branches and spiral around us. She laughs, delighted, then looks at Sky, the happiness fading from her eyes.

"Oh, I'm sorry," she says to her, remorsefully. "I wasn't thinking."

Sky shrugs and stares at the ground. "It's yours now," she answers quietly. "Do whatever you want with it."

The leaves fly back towards the trees and Iris rests a hand on Sky's arm. "Don't be angry, Sky," she says pleadingly. "I didn't mean to steal your power, I promise."

"I'm not angry," mutters Sky, not looking up. "Well, maybe a little, but I deserve it, I know."

"I'm sorry," Iris repeats. She holds out her hands. "Look, I'll try and give it you back-"

"Why should you be sorry?" I ask her. Anger rises in me again. "You're the one who can barely stand!"

Sky bites her lip, then her eyes darken too. "Look, I know I shouldn't have done what I did, but don't you think I've already paid for it? I need my power! Magic was the only thing that kept me sane when my entire world crumbled! I've lost everything... Everything that made me me."

"And Iris nearly lost her life!" I fire back.

"Cressida!" says Iris, reading my mind. "Both of you! Shut up arguing, it's over now!"

"Magic was my life!" Sky cries furiously.

"Then your life wasn't worth much," I say flatly, shoving my guilt to the back of my mind.

"Sky!" Iris yells out, horrified, as Sky moves wrathfully towards me. A transparent lilac shield bursts from her hands, stopping Sky from getting any closer. Sky stops and glares at me through the wall, and I glare back. When Iris is convinced that neither of us are going to attack each other, she lowers the shield.

"How could I possibly expect you to understand?" Sky shouts at me, barely noticing that the barrier is gone. "You're ordinary! You've never had magic! You have no idea how this feels!"

"Maybe not," I say, my breathing fast and angry. "But I know that the life of a friend is worth more than all the magic in the world."

Before I can react, Sky is racing towards me, her blue eyes icy with rage. I cry out, stepping backwards, but instead she throws herself to the ground and grabs my satchel, which is lying a few feet away. I hadn't even noticed that it has fallen off. Then suddenly Sky is running down the hill, her blonde hair and cloak flying behind her, taking my satchel and Iris's mirror with her.

"Sky!" Iris shrieks after her, trying to follow, but she's still too weak to run. All we can do is watch as she keeps running, until she's just a tiny dot far below us. And although the anger still boils inside me, I feel strangely hollow as I watch her fade from view. Still, there's nothing we can do. Sky's made her choice, so fine. We'll go on without her. I pull up my sleeve and inspect my forearm, and the mark of the mortem glowers up at me, starting to blacken around the edges, a deadly clock counting down the hours I have left.

"Iris," I say abruptly, turning away from the view. "How do we find the healing plant? Do you know where it is?"

Iris drags a hand over her eyes and reaches for my hand. And suddenly, we're standing at the entrance of a narrow, cobbled street, with conveniently few people around. I shake my head, dizzy from the journey.

"Sorry," says Iris quietly. "I'm still getting used to magic."

"It's fine, you're doing great. Where are we?" I ask her.

Iris takes a calming breath. "I'm not sure where the tempus plantandi is, and it's very rare. I've brought us to the nearest apothecary's. Now we can find out where it is and how to use it." She gives me a sideways look and opens her mouth to say something, but senses that I don't want to talk about it. I give her a grateful smile then enter a small, shabby-looking building to our left, with a rusty sign that says Apothecary's: Medicines and Herbs.

The inside of the shop is somehow even smaller than it looks from the outside. As soon as we step inside, we have to carefully manoeuvre ourselves to avoid crashing into the shelves on the walls and knocking their contents- glass jars of strange liquids, herbs and, disgustingly, animal parts- to the ground. We don't even have to take three steps to reach the counter, behind which stands a relatively old man. He peers short-sightedly at us through black, tunnel-like eyes, strings of grey hair hanging limply around his face, which is surprisingly sharp and shrewd. Behind him I can see a dusty shelf of leather bound books, and a set of rusty iron stairs that must lead to the cellars.

"What brings you two young ladies here?" asked the man in a creaking voice, pulling his long sleeves over his wrists.

I clear my throat. "Hello. Um, do you know where we can find the tempus plantandi, please?"

The man stares at us quizzically, suddenly alert with interest. His eyes dart towards my left arm, and I automatically pull my sleeve down further. Then he pulls a thick book off the shelf behind it and flicks it open to a page near the back, resting it on the counter. Iris and I lean over it. The chapter on the tempus plantandi barely takes up quarter of a page.

"The herb you speak of is very rare," rasps the apothecary. "Experts believe that there is only one left in existence. They grow mostly in extremely high places, so many people suffering from the horologium mortem, who are in need of the healing properties of this plant, are unable to make the journey."

I bend over to read the part spidery print. The tempus plantandi is most commonly found at the highest peak of mountains, facing the east to gain more sunlight. When treating the horologium mortem, crush the bloom of the tempus plantandi and mix it with water until you are left with a thick, magenta liquid. The invalid must consume the liquid and, upon doing so, their condition should be healed within a few minutes.

Seeing as Sky ran off with the jewellery in my satchel, we can't afford to buy the book, so I commit the passage to memory. Thanking the apothecary, we leave the shop.

"I'll take us to the highest mountain," Iris tells me, taking my hand. "Are you ready?"

I nod, and just like that, we're gone.