Alex’s mouth crinkled up into a smile. “They’re guide-stones,” he said. “The Masters are having a meeting tonight. You’re invited.” He wiggled his fingers. “One stone for each of you.”

“We’re invited?” Aaron said as the three of them plucked the stones out of Alex’s hand. He looked nervous. “Why?”

“Search me. I’m just the messenger.”

“So what do we do with these?” Call asked, examining his stone. Perfectly round and shiny, it did look a lot like a red marble. The big ones that you shot with.

“The Masters have been moving their meetings around to preserve security,” said Alex. “Unless you have one of these, you can’t find the room. The meeting starts at six — just let the stone take you where you’re supposed to go.”

Six o’clock found the three of them sitting in their new common room with Havoc, staring at the stones in their hands. They were all dressed in their blue school uniforms; Aaron had polished his shoes and Tamara had her hair down, gold barrettes clipped above her ears. Call’s concession to fanciness was washing his face.

“Whoa!” Tamara said as her guide-stone lit up like a tiny Christmas light. Aaron’s followed, flickering, and then Call’s. They all stood.

“Havoc, stay here,” Call told his wolf. After the previous meeting with the Assembly, he didn’t want to give them any excuse to remember Havoc’s existence.

Out in the hall, Tamara was using her stone to navigate. When she turned in the wrong direction, the glow of the stone dimmed.

“Master Rufus should have given us one of these when we went into the tunnels,” Call said as they set off. “Instead of that vanishing map.”

“I think that would have defeated the purpose of the lesson,” Aaron pointed out, folding his fingers over his stone so he didn’t have to keep squinting into its light. “You know, about finding your own way.”

“Don’t be superior,” Tamara said, making an abrupt turn. All of their stones went to half-light.

“I think you, uh, missed the turn,” Call said, pointing backward, into the large room with an underground waterfall that the stone seemed to indicate they should be heading into.

“Come on,” she said, scrambling ahead, leaving Aaron and Call nothing to do but follow.

She ducked into the small entryway that led to a space with high ceilings and a small group of bats huddled together, making little nickering noises to one another. The whole room stank of them. Call pinched his nose.

“What are you doing, Tamara?” Aaron asked, voice low.

She hunched down and crawled into a tight passageway. Call and Aaron traded worried looks. It was dangerous to explore the caves without a map or a guide of some kind. There were deep pits and boiling lakes of mud, not to mention elementals.

Heading into the passageway after Tamara, Call really hoped she knew where she was going.

The rock was rough under his hands as he crawled along what seemed to be a naturally forming tunnel. It narrowed, and Call wasn’t sure they were going to fit through. His heart began to thud as their only light faded dimmer and dimmer. After a few tense minutes, the area opened up into an unfamiliar but not particularly dangerous-looking room. Their stones brightened.

“Are you going to explain what all of that was about?” Call demanded.

Tamara put her hands on her hips. “We have no idea who’s after you. It might be one of the Masters or someone who knows where the meeting is being held. We can’t go the direct route. There might be a trap. The whole point of stones like these is to make sure we can’t get lost.”

“Oh, that’s smart,” Call said, trying to ignore the cold dread pooling in his stomach. He wanted to believe that whoever his enemy or enemies were, they weren’t the current Masters at the school. He wanted to believe it was just some sneaky minion of Master Joseph or some random miserable Makar-hating mage. Or maybe a student who Call had annoyed in a big way. Call knew he could be really annoying, especially when he was putting effort into it.

Call was still mulling it all over when they arrived at the room the Masters had chosen for the meeting. They were late and the session had already begun. A group of Masters in black sat around a semicircle of smoothly polished marble. A long, low marble bench ran across the outside of the semicircle, allowing the Masters to face the center of the room. The stalactites that hung from the ceiling ended in round pendant bulbs of clear stone, each one glowing with a yellowish light.

“Tamara, Aaron, and Call,” Master Rufus intoned as they filed into the room. “Please take your seats.”

He indicated three heaps of jumbled polished rocks directly in front of the Masters’ table. Call stared. Were they supposed to sit on those? Wouldn’t the rocks just scatter, depositing them each onto the floor in an embarrassing pile?

But Tamara brushed past him confidently and sat on one of the rock heaps. She sank down slightly and crossed her arms, but the rocks didn’t scatter. Aaron followed and Call went after him, throwing himself down on a rock pile. The stones hissed and clattered as his weight displaced them, but it was like sitting in a chair made out of taffy, though less sticky — the rocks molded and reformed around him until he was sitting as comfortably as his leg would allow.

“Cool!” Call exclaimed. “We need one of these in our common room.”

“Call,” Rufus said darkly. Call had the feeling Master Rufus still thought he knew something he wasn’t saying. “Please restrain your commentary on the furniture; this is a meeting.”

Really? I thought it was a party! Call wanted to say but didn’t. Definitely, there couldn’t have been less of a party atmosphere. Master North and Master Milagros flanked Rufus; Anastasia Tarquin, her steely silver hair piled on her head, sat near the end of the table, her dark gaze fixed on Call.

“What’s this about?” Aaron asked, looking around the room. “Are we in trouble?”

“No,” said Master Milagros at the same time that Master North said, “Maybe,” and snorted.

“We’re just trying to reason out how this attack could have happened,” said Master Milagros with a sideways look in Anastasia’s direction. “We had so many safeguards in place. We know you’ve gone through what happened before, but can you tell us all one more time, for the record?”