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 na**d 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.