“Go ahead,” said Master Rufus. “Get in.”

Aaron scrambled into the first of the boats, reaching out his hand to help Call inside. Resentfully, Call took it. Tamara got in behind them, looking a little nervous herself. As soon as she was settled, Master Rufus stepped into the boat.

“This is the most common way we get around the Magisterium, using the underground rivers. Until you can navigate, I will take you through the caves. Eventually, each of you will learn the paths and how to coax the water to take you where you want to go.”

Master Rufus leaned over the side of the boat and whispered to the water. There was a soft ripple across the surface, as if the wind had stirred it, even though there was no wind underground.

Aaron leaned forward to ask another question, but all at once, the boat began to move and he fell back into his seat.

Once, when Call had been a lot younger, his father had taken him to a big park with rides that started like this. He’d cried through all of them, totally terrified, despite the cheerful music and the animated dancing puppets. And those had been rides. This was real. Call kept thinking about bats and sharp rocks and how, sometimes, in caves, there were cliffs and holes that dropped down like a million feet below sea level. How were they going to be able to avoid stuff like that? How were they going to know if they were going the right way in the dark?

The boat cut through the water, into darkness. It was the darkest darkness Call had ever experienced. He couldn’t even see his hand in front of his face. His stomach lurched.

Tamara made a tiny sound. Call was glad it wasn’t just him who was freaked out.

Then, all around them, the cave came to glowing life. They passed into a room where the walls shimmered with pale, bioluminescent green moss. The water itself turned to light where the prow of the boat touched it; when Aaron dragged his hand through the river, it lit around his fingers, too. He flicked water into the air and it transformed into a cascade of sparks. “Cool,” Aaron breathed.

It was kind of cool. Call started to relax as the boat slipped silently through the glowing water. They passed walls of rock striped in dozens of colors, and rooms where long pale vines hung from the ceiling, trailing tendrils in the river. Then they would slide again into a dark tunnel and emerge into a new stone chamber where quartz stalactites sparkled like knife blades, or where the stone seemed to grow naturally into the shapes of curved benches, even tables — they passed two silent Masters in one chamber, playing checkers with pieces that flew through the air. “Got you!” said one of them, and the wooden discs started to rearrange themselves, resetting the board to the beginning.

As though it were being steered by some invisible hand, the boat docked itself near a small platform with stone steps, rocking gently in place.

Aaron was out of the boat first, followed by Tamara, and then Call. Aaron reached out a hand to help him, but Call deliberately ignored it. He used his arms to flip himself over the side of the boat, landing awkwardly. For a moment, he thought he was going to fall backward into the river, making a huge bioluminescent splash. A large hand clamped down on his shoulder, steadying him. He looked up in surprise to see Master Rufus watching him with a strange expression.

“I don’t need your help,” Call said, startled.

Rufus said nothing. Call couldn’t read his expression at all. He took his hand off Call’s shoulder.

“Come,” he said, and stalked up a smooth path that cut through the pebbly shore. The apprentices scrambled to follow.

The path led up to a blank granite wall. When Rufus put his hand to the stone, it turned transparent. Call wasn’t even surprised. He’d come to expect weirdness. Rufus walked through the wall as if it were made of air. Tamara ducked after him. Call looked at Aaron, who shrugged. Taking a deep breath, Call followed.

He emerged into a chamber whose walls were bare rock. The floor was completely smooth stone. In the center of the room was a pile of sand.

“First, I wish to go over the Five Principles of Magic. You may remember some of these from your first lecture on the bus, but I don’t expect any of you — even you, Tamara, no matter how many times your parents have drilled you — to truly comprehend them until you have learned many more things. You may write these down, however, and I do expect you to think on them.”

Call scrambled with his pack and tugged out what appeared to be a hand-stitched notebook and one of those annoying pens from the Trial. He shook it lightly, hoping it wasn’t going to explode this time.

Master Rufus began to speak and Call scrambled to transcribe fast enough. He wrote:

1. Power comes from imbalance; control comes from balance.

2. All elements act according to their nature: Fire wants to burn, water wants to flow, air wants to rise, earth wants to bind, chaos wants to devour.

3. In all magic, there is an exchange of power.

4. You can change a thing’s shape, but not its essential nature.

5. All elements have a counterweight. Fire is the counterweight of water. Air is the counterweight of earth. The counterweight of chaos is the soul.

“During the tests,” said Master Rufus, “all of you displayed power. But without focus, power is nothing. Fire can either burn down your house or warm it; the difference is in your ability to control the fire. Without focus, working with the elements is very dangerous. I don’t need to tell some of you just how dangerous.”

Call looked up, expecting to be the one who Master Rufus was staring at, since Master Rufus seemed to always be looking at Call when he said something ominous. This time, however, he was looking at Tamara. Her cheeks flushed and her chin went up defiantly.

“Four days a week, you three will train with me. On the fifth day, there will be a lecture by one of the other mages, and then, once a month, there will be an exercise in which you will put what you have learned to use. On that day, you may find yourselves either competing against or working with other apprentice groups. Weekends and nights are yours for practice and further study. There is the Library as well as practice rooms, and the Gallery, where you can waste time. Do you have any questions for me before we begin your first lesson?”

No one spoke. Call wanted to say something about how he’d love some directions to that Gallery place, but he held himself back. He remembered telling his father back at the hangar that he was going to get himself thrown out of the Magisterium, but he’d woken up that morning with the sinking feeling that maybe that wasn’t such a good idea. Trying to flunk the tests in front of Rufus hadn’t worked, after all, so acting out might not either. Master Rufus clearly wasn’t going to let him communicate with Alastair until Call settled in as an apprentice. As much as it galled him to do it, he probably had to be on his best behavior until Rufus relaxed and let him contact his father. Then, when he could finally talk to Alastair, they’d plan his escape.

He just wished he felt a little more enthusiastic about running away.

“Very well. Can you guess why I’ve set up the room this way, then?”

“I’m guessing you need help fortifying your sand castle?” muttered Call under his breath. Even his best behavior apparently wasn’t all that good. Aaron, standing beside him, stifled a laugh.

Master Rufus raised a single brow but didn’t otherwise acknowledge what Call had said. “I want you three to sit in a circle around the sand. You can sit any way that you’re the most comfortable. Once you’re ready, you must concentrate on moving the sand with your mind. Feel the power in the air around you. Feel the power in the earth. Feel it rise up through the soles of your feet and in the breaths you take. Now focus it. Grain by grain, you are going to separate the sand into two piles — one dark and one light. You may begin!”