CALL WOKE THE next day scared that Master Rufus would say something about the scattered papers, wrecked model, and missing envelope in his office … and even more scared that he would say something about the missing elemental. He dragged his heels all the way to the Refectory, but when he got there, he overheard a heated argument between Master Rufus and Master Milagros.

“For the last time, Rufus,” she was saying in the tone of someone much aggrieved, “I don’t have your lizard!”

Call didn’t know whether to feel bad or laugh.

After breakfast, Rufus led them down to the river, where he instructed them to practice picking up water, tossing it into the air, and catching it without getting wet. Pretty soon Call, Tamara, and Aaron were breathless, laughing, and soaked. By the time the day was over, Call was exhausted, so exhausted that what had happened the day before seemed distant and unreal. He headed back to his room to puzzle over his father’s letter and the wristband but was sidetracked by the fact that Warren had eaten one of his shoelaces, slurping it up like a noodle.

“Dumb lizard,” he muttered, hiding the armband he’d worn in the wyvern exercise, and the crumpled letter from his father, in the bottom drawer of his desk and shoving it closed so the elemental wouldn’t eat them, too.

Warren said nothing. His eyes had gone a grayish color; Call suspected the shoelace was disagreeing with him.

The biggest distraction from trying to puzzle out what his dad had meant turned out, to Call’s surprise, to be his classes. There was no more Room of Sand and Boredom; instead, there was a roster of new exercises that made the next few weeks go by quickly. The training was still hard and frustrating, but as Master Rufus revealed more of the magical world, Call found himself growing increasingly fascinated.

Master Rufus taught them to feel their affinity with the elements and to better understand the meaning behind what he called the Cinquain, which, along with the rest of the Five Principles of Magic, Call could now recite in his sleep.

Fire wants to burn.

Water wants to flow.

Air wants to rise.

Earth wants to bind.

Chaos wants to devour.

They learned how to kindle small fires and to make flames dance on their palms. They learned to make waves in the cave pools and call over the pale fish (although not to operate the boats, which continued to annoy Call to no end). They even began to learn Call’s favorite thing — levitating.

“Focus and practice,” Master Rufus said, leading them to a room covered with bouncy mats stuffed with moss and pine needles from the trees outside the Magisterium. “There are no shortcuts, mages. There’s only focus and practice. So get to it!”

They took turns trying to draw energy from the air around them and use it to push themselves upward from the soles of their feet. It was much harder to balance than Call would have thought. Over and over, they fell giggling onto the mats, on top of one another. Aaron wound up with one of Tamara’s pigtails in his mouth, and Call with Tamara’s foot on his neck.

Finally, almost at the end of the lesson, something clicked for Call, and he was able to hover in the air, a foot above the ground, without wobbling at all. There was no gravity pushing down on his leg, nothing that might keep him from soaring sideways through the air except his own lack of practice. Dreams of the day that he could fly through the halls of the Magisterium far faster than he could ever have run exploded through his head. It would be like skateboarding, only better, faster, higher, and with even crazier stunts.

Then Tamara crossed her eyes at him and he lost his concentration and thumped back to the mat. He lay there for a second, just breathing.

For those moments that he’d hung in the air, his leg hadn’t hurt, not even a little.

Neither Tamara nor Aaron had managed to get really airborne before the end of the lesson, but Master Rufus seemed delighted with their lack of progress. Several times, he declared it to be the funniest thing he’d seen in a long while.

Master Rufus promised them that by the end of the year, they’d be able to call up a blast of each element, walk through fire, and breathe underwater. In their Silver Year, they would be able to call on the less evident powers of the elements — to shape air into illusions, fire into prophecies, earth into bindings, and water into healing. The thought of being able to do those things thrilled Call, but whenever he thought of the end of the year, he recalled the words of his father’s note to Rufus.

You must bind Callum’s magic before the end of the year.

Earth magic. If he made it to his Silver Year, maybe he’d learn what binding things entailed.

In one of the Friday lectures, Master Lemuel taught them more about counterweights, warning them that if they overextended themselves and felt themselves being drawn into an element, they should reach for its opposite, just as they had reached for earth when battling an air elemental.

Call asked how you were supposed to reach for soul, since that was the counterweight of chaos. Master Lemuel snapped that if Call were battling a chaos mage, it wouldn’t matter what he reached for, because he’d be about to die. Drew gave him a sympathetic look. “It’s okay,” he said, under his breath.

“Stop that, Andrew,” said Master Lemuel in a frozen voice. “You know, there was a time when apprentices who failed to show respect to their Masters were whipped with saplings.”

“Lemuel,” said Master Milagros anxiously, noting the horrified looks on the faces of her own students, “I don’t think —”

“Unfortunately, that was centuries ago,” said Master Lemuel. “But I can assure you, Andrew, that if you keep whispering behind my back, you’ll be sorry you ever came to the Magisterium.” His thin lips curled into a smile. “Now come up here and demonstrate how you reach for water when you’re using fire. Gwenda, if you would come up to assist him with the counterweight?”

Gwenda walked to the front; after hesitating, Drew shuffled up beside her, his shoulders hunched. He endured twenty minutes of merciless teasing from Lemuel when he couldn’t extinguish the flame in his hand, even though Gwenda was holding out a bowl of water to him with so much hopeful enthusiasm that some of it slopped onto his sneakers. “Come on, Drew!” she kept whispering until, eventually, Master Lemuel told her to be quiet.

It made Call appreciate Master Rufus more, even when he gave them a lecture about the duties of mages, most of which seemed really obvious, like keeping magic a secret, not using magic for personal gain or evil ends, and sharing all knowledge gleaned from magical study with the rest of the mage community. Apparently, mages who’d achieved mastery in their study of the elements were required to take apprentices as part of that “sharing all knowledge” thing — meaning there were different Masters at the Magisterium at different times, though those who’d found their vocation as teachers were there permanently.

Being forced to take apprentices explained a lot about Master Lemuel.

Call was more interested in Master Rockmaple’s second lecture about elementals. Mostly, it turned out, they weren’t sentient creatures. Some kept the same shapes they’d held for centuries, while others fed on magic to become large and dangerous. A few had even been known to absorb wizards. It made Call shudder to think of Warren after hearing that. What had he let loose in the Magisterium? What exactly was sleeping above his bed and eating his shoelaces?

Call learned more about the Third Mage War, too, but none of it gave him any more idea why his father wanted Call’s magic bound.

Tamara laughed more as time went on, often with a guilty look, while, oddly, Aaron became more serious as the three of them settled more and more into the Magisterium. Call felt he’d learned his way around and was no longer afraid of getting lost on his way to the Library, the classrooms, or even the Gallery. Nor did he think it was weird anymore to eat mushrooms and piles of lichen that tasted like delicious roasted chicken or spaghetti or lo mein.

He and Jasper still kept their distance, but Celia stayed his friend, acting like nothing weird had happened that night.

Call began to dread the end of the year, when his father would want him to come home for good. He had real friends for the first time in his life, friends who didn’t think he was too weird or messed up because of his leg. And he had magic. He didn’t want to give any of it up, even though he’d vowed he would.

It was hard to keep track of seasons passing underground. Sometimes, Master Rufus and the other Masters would take them outside for various earth exercises. It was always kind of cool to see what the other students were good at — when Rufus showed them how to blend elemental magic to make plants grow, Kai Hale made a single seedling sprout and grow so huge that the next day, Master Rockmaple had to come out with an axe and chop it down. Celia was able to summon animals from underground (though not, to Call’s disappointment, any naked mole rats). And Tamara was amazing at using the magnetism of the earth to find paths when everyone got lost.

As the outside world started to catch fire in fall colors, the caves grew colder. Big metal bowls full of hot stones lined the corridors, heating the air, and a blazing fire was always in the Gallery now when they went there to watch movies.

The cold didn’t bother Call. He felt as if he was getting tougher somehow. He was fairly sure he had grown at least an inch. And he could walk farther, despite his leg, probably because Master Rufus was fond of taking them on hikes through the caverns, or bouldering among the big rocks aboveground.

At night sometimes, Call would take out the wristband from the bedside table and read over both letters from his dad. He wished he could tell his father about the things he was doing, but he never did.

They were well into winter when Master Rufus announced that it was time they started exploring the caves on their own, without his assistance. He’d already shown them how to find their way among the deeper caverns by using earth magic to light up individual rocks and create a path back.

“You want us to get lost on purpose?” Call asked.

“Something like that,” said Rufus. “Ideally, you will follow my instruction, find the room you are meant to find, and return without getting lost at all. But that part is up to you.”

Tamara clapped her hands together and smiled a slightly devilish smile. “Sounds like fun.”

“Together,” Master Rufus told her. “No running off and leaving those two stumbling around in the dark.”

Her smile dimmed a little. “Oh, okay.”

“We could make a bet,” Call said, thinking of Warren. If he could use some of the shortcuts the lizard had shown him, he might out-navigate her. “See who finishes first.”

“Did either of you hear me?” Master Rufus asked. “I said —”

“Together,” said Aaron. “I’ll make sure we stick by each other.”

“See that you do,” said Master Rufus. “Now, here is your assignment. At the depths of the second level of the caves is a place called the Butterfly Pool. It’s fed from a spring aboveground. The water there is heavy with minerals that make it excellent for smithing weapons, like that knife on your belt.” He gestured to Miri, making Call touch the hilt self-consciously. “That blade was made here, in the Magisterium, with water from the Butterfly Pool. I want the three of you to find the room, gather some of the water, and return to me here.”

“Do we get a bucket?” Call asked.

“I think you know the answer to that, Callum.” Rufus drew a rolled-up parchment from his uniform and handed it to Aaron. “Here is your map. Follow it closely to reach the Butterfly Pool, but remember to light stones to mark your way. You can’t always rely on a map to bring you back.”

Master Rufus settled down on a large boulder, which gently shaped and reformed itself underneath him until it resembled an armchair. “You will take turns carrying the water. If you drop it, then you’ll just have to return for more.”

The three apprentices exchanged glances. “When do we start?” asked Aaron.

Master Rufus drew a heavy bound book from his pocket and began to read. “Immediately.”

Aaron spread the paper out on a rock in front of him, scowling, then looked over at Master Rufus. “Okay,” he said quickly. “We head down and east.”

Call crowded close, looking at the map over Aaron’s shoulder. “Past the Library looks like the quickest way.”

Tamara turned the map with a smirk. “Now north is actually pointing north. That should help.”

“Library’s still the right way,” Call said. “So it didn’t help that much.”

Aaron rolled his eyes and stood, folding the map. “Let’s go, before you two get out compasses and start measuring distances with string.”

They headed out, at first going through the familiar parts of the cave. They passed into the Library, following its spirals down, like navigating the inside of a nautilus shell. The very bottom led out into the lower levels of the caves.

The air grew heavier and colder and the smell of minerals hung thick in the air. Call felt the change immediately. The passageway they were in was cramped and narrow, the roof low overhead. Aaron, the tallest of the three, almost had to bend down to walk along it.

Finally, the passageway opened out into a larger cavern. Tamara touched one of the walls, lighting up a crystal and illuminating the roots. They hung down in creepy, spidery vines to almost touch the tops of a vivid orange stream that smoked sulfurously, filling the room with a burnt odor. Massive mushrooms grew along the sides of the stream, striped in unnaturally bright greens and turquoises and purples.

“I wonder what would happen if we ate them?” Call mused as they picked their way among the plants.

“I wouldn’t try it to find out,” said Aaron, raising his hand. He had taught himself to make a ball of glowing blue fire the week before and was very excited about it. He was constantly making balls of glowing fire, even when they didn’t need light or anything. He held the fire up in one hand, and the map in the other. “That way,” he said, gesturing to a passage off to the left. “Through the Root Room.”

“The rooms have names?” Tamara said, stepping gingerly around the mushrooms.

“No, I’m just calling it that. I mean, we won’t forget it if it has a name, right?”

Tamara furrowed her brow, considering. “I guess.”

“Better than Butterfly Pool,” Call said. “I mean, what kind of name is that for a lake that helps make weapons? It should be called Killer Lake. Or the Pond of Stabbings. Or Murder Puddle.”

“Yeah,” Tamara said drily. “And we can start calling you Master Obvious.”

The next chamber had thick stalactites, white as giant shark’s teeth, clumped together as though they might really be attached to the jaw of some long-buried monster. Passing beneath this scarily sharp overhang, Call, Aaron, and Tamara next walked through a narrow, circular opening. Here, the rock was pocked with cave formations that looked eaten away, as though they were in some kind of oversize termite nest. Call concentrated and a crystal in the far corner began to glow, so they wouldn’t forget they’d been this way.

“Is this place on the map?” he asked.

Aaron squinted. “Yeah. In fact, we’re almost there. Just one room to the south …” He disappeared through a dark archway, then reappeared a moment later, flushed with victory. “Found it!”

Tamara and Call crowded in after him. For a moment, they were silent. Even after seeing all sorts of spectacular underground rooms, including the Library and the Gallery, Call knew he was seeing something special. From a gap high in one wall, a torrent of water poured out, splashing down into a huge pool that glowed blue, as if lit from the inside. The walls were feathery with bright green lichen, and the contrast of the green and the blue made Call feel as if he were standing inside a huge marble. The air was redolent with the odor of some unfamiliar and tantalizing spice.

“Huh,” Aaron said after a few minutes. “It is kind of weird that it’s called the Butterfly Pool.”

Tamara walked up to the edge. “I think that’s because the water is the color of those blue butterflies — what are they called?”

“Blue monarchs,” Call said. His father had always been a fan of butterflies. He had a whole collection of them, pinned under glass over his desk.

Tamara put her hand out. The pool shuddered, and a sphere of water rose up from it. Even as it shifted and rippled across the surface, it kept its shape.

“There,” Tamara said, a little breathlessly.

“Great,” said Aaron. “How long do you think you can hold it?”

“I don’t know.” She tossed back a thick dark braid, trying not to let any strain show on her face. “I’ll tell you when my concentration starts to give.”

Aaron nodded, smoothing the map out against one of the damp walls. “Now we just need to find our way —”

At that moment, the map in his hands burst into flames.

Aaron yelled and pulled his fingers away from the blackening pages sparking through the air. The pages fell in a shower of embers and hit the floor. Tamara yelped, losing her focus. The water she’d been suspending splashed down over her uniform and turned into a puddle at their feet.

The three of them looked at one another, wide-eyed. Call straightened his shoulders. “I guess that’s what Master Rufus meant,” he said. “We’re supposed to follow our lighted stones or marks or whatever in order to get back. That map was only good for the way here.”

“Should be easy,” Tamara said. “I mean, I only lit one of them, but you guys lit more, right?”

“I lit one, too,” said Call, looking hopefully in Aaron’s direction. Aaron didn’t look back.

Tamara frowned. “Ugh, fine. We’ll figure out the way back. You carry the water.”

With a shrug, Call went over to the lake and concentrated on shaping a ball. Call drew on the air around him to move the water and felt the push-pull of the elements inside him. He wasn’t as good at it as Tamara, but he did okay. His ball dripped only a little as it hovered.

Aaron frowned and pointed. “We came in there. This way. I think …”

Tamara followed Aaron, and Call went after her, the ball of water spinning over his head as if he had his own personal storm cloud. The next room was familiar: the underground stream, the colorful mushrooms. Call navigated among them carefully, afraid that at any moment his water ball would fall directly on his head.

“Look,” Tamara was saying. “There’s lit-up stones over here….”

“I think those are just bioluminescence,” Aaron said in a worried voice. He tapped at them and then turned back to her with a shrug. “I don’t know.”

“Well, I do. We go this way.” She set off with a determined stride. Call followed, left-right-left, through a cavern full of huge stalactites growing in the shapes of leaves, don’t drop the water, around a corner, through a gap between boulders, keep it together, Call. There were sharp rocks all around and Call nearly walked right into a wall because Tamara and Aaron had stopped dead. They were arguing.

“I told you it was just glowing lichen,” Aaron said, clearly frustrated. They were in a large room with a stone cistern in the center, bubbling gently. “Now we’re lost.”

“Well, if you’d remembered to light up stones as we went —”

“I was reading the map,” Aaron said, exasperated. In a way, Call thought, it was kind of nice to know that Aaron could get irritated and unreasonable. Then Aaron and Tamara turned to glare at Call, and Call nearly dropped the spinning globe he’d been balancing. Aaron had to throw out a hand to stabilize the water. It hovered in the air between them, shedding droplets.

“What?” Call said.

“Well, do you have any idea where we are?” said Tamara.

“No,” Call admitted, glancing around at the smooth walls. “But there must be some way to find our way back. Master Rufus wouldn’t just send us down here to get lost and die.”

“That’s pretty optimistic, coming from you,” said Tamara.

“Funny.” Call made a face to show her exactly how funny it wasn’t.

“Stop it, both of you,” Aaron said. “Arguing isn’t going to get us anywhere.”

“Well, following you is going to get us somewhere,” Call said. “And that somewhere is about as far away as you can get from where we need to be.”

Aaron shook his head, disappointed. “Why do you have to be such a jerk?” he asked Call.

“Because you never are,” Call told him staunchly. “I have to be a jerk for both of us.”

Tamara sighed and then, after a moment, laughed. “Can we admit that we’re all at fault? We all messed up.”

Aaron looked like he didn’t want to admit it, but finally he nodded. “Yeah, I forgot that we weren’t allowed to use the map on the way back.”

“Yeah,” said Call. “Me, too. Sorry. Aren’t you good at finding paths, Tamara? What about all that tapping into the metal of the earth stuff?”

“I can try,” Tamara said, her voice a little hollow. “But that just lets me know which way north is, not how these passageways intersect. But we’ve got to come across something familiar eventually, right?”

It was scary to think about wandering through the tunnels, to think about the pits of darkness they could fall into, the sucking mud pools and the weird choking steam rising from them. But Call didn’t have a better plan. “Okay,” he said.

They began to walk.

This was pretty much exactly what his father had warned him about.

“You know what I miss from home?” Aaron asked as they went, picking their way past concretions that looked like tattered tapestries. “It’s going to sound super lame, but I miss fast food. Like the greasiest possible burger and a mound of fries. Even the smell of them.”

“I miss lying out in the backyard in the grass,” Call said. “And video games. I definitely miss video games.”

“I miss wasting time online,” Tamara said, surprising Call. “Don’t give me that face — I lived in a town just like the kind you guys grew up in.”

Aaron snorted. “Not like where I grew up.”

“I mean,” she said, taking over the maintenance of the spinning blue globe of water, “I grew up in a town full of people who weren’t mages. There was a bookshop where the few mages met up or left messages for one another, but other than that, it was normal.”

“I’m just surprised your parents let you go online,” Call said. It was such a regular, non-fancy way to waste time. When he imagined her outside the Magisterium, having fun, he imagined her riding a polo pony, although he wasn’t exactly sure what that was or how it was different from a regular pony.

Tamara smiled at him. “Well, they didn’t exactly let me….”

Call wanted to know more about that, but as he opened his mouth to ask, his breath caught at the sight of the remarkable room that had just appeared in front of him.