He turned back to the chalkboard, erased his name, and wrote in imposing letters: DON’T TAKE CANDY FROM STRANGERS!

Nate squirmed.

“Now, that may not seem like news to anyone,” Mr. Dart said. “This message, in various forms, has been drilled into children across many cultures for centuries. Why do you suppose this message gets repeated?”

April Flynn raised her hand. Mr. Dart nodded at her.

“Because strangers might lure you into their car to kidnap you,” April said.

“A common response, and a real threat,” Mr. Dart said. “Or maybe the stranger tampered with the candy and made it unsafe. I want to propose a lesser known reason. There are magicians in the world who are capable of creating powerful spells that work only on children. They blend these enchantments with candy to entice youngsters. These magicians consider children a disposable resource. They put kids in danger, get what they can from them, and then cast them aside when their usefulness has passed. None of these magicians can be trusted. They are not a new phenomenon. Some of the oldest children’s tales contain warnings about them. Who knows the story of Hansel and Gretel?”

Several hands went up.

John Dart continued as if he had not asked the question. “Two children get lost in the woods and stumble upon a delicious house made of candy. Attracted by the sweets, the kids are captured by a witch, who continues feeding them treats. Why? The witch is fattening them up so she can eat them.”

Mr. Dart paused, staring at Nate, who dropped his gaze to his hands.

“Moral of the story? Don’t take candy from strangers. You can find similar warnings in other tales. My message today is: Do not trust magicians who exploit children for gain.”

Walt Gunther timidly raised his hand. Mr. Dart nodded at him.

“Are you sort of making up a fairy tale?” he asked, sounding concerned that Mr. Dart might be insane.

Mr. Dart smiled. “Something like that. I’m trying to prove a point to anyone who might be feeling confused about the issue. If any of you want to talk with me more on the subject, I’ll be at my desk. Otherwise, find a task to perform quietly.”

Mr. Dart returned to the desk and sat down. He took out a pen and began writing in a notebook.

Nate tapped his desk nervously with his pen. Whatever Mr. Dart was doing here, it was clear that he knew about the magicians and the candy. There was no point in trying to act naive. The man was on to them. It would be better to confront him directly. Mustering his courage, Nate got up and walked to the front of the room.

Mr. Dart looked up from his notebook. “Pull up a chair.”

Nate grabbed a chair, glancing over at Summer and Pigeon. Summer pointed at herself and then at Mr. Dart. Nate shook his head. He did not want Summer or Pigeon to reveal themselves until he learned more about the unexpected substitute.

Nate sat down by Mr. Dart. “Do you know me?” Nate asked quietly.

“I do,” Mr. Dart said in a deep, hard voice. “I don’t know all the details, but I know you’re in way over your head. If you’ll fill me in, I can help.”

“How do I know you’re different from any of the other magicians?”

Mr. Dart almost smiled. “First of all, I’m no magician. Second, I’m not after what they’re after. I’m only here to stop them. Third, unlike them, I’ll tell you everything I know once I’m convinced you’re on my side.”

Nate rubbed his knees. “If that’s all true, I may talk to you. But first you need to prove yourself.”

Mr. Dart leaned back in his chair, thick fingers brushing the brim of his hat. “Look, I wouldn’t be here if I didn’t have a hunch you were basically a good kid. Belinda can be sly. She could cajole an honest kid into serving her. It seems clear you caught on to what she really is and that you were trying to fight back. Without help, it’s a fight you’ll lose. My guess is you’re involved with Sebastian as well.”

“He seems like a pretty good guy,” Nate said.

Mr. Dart exhaled sharply, not quite a chuckle. “Compared to Belinda, yes, he is the lesser of two evils. But I expect he is keeping secrets, just as she did. Has he even told you what he is after?”

“An ancient treasure,” Nate said.

“What ancient treasure?”

Nate shrugged.

“Do you understand that most of the treats these magicians prepare for you would not work on themselves? They’re too old. It’s the catch-22 of magic.”

“Mr. Stott explained that.”

“Do you understand that the unattainable miracle all magicians pursue is the ability to reduce their age? They can prolong their years, but they can’t make themselves a second younger. If these wise old magicians could only turn back the clock, their power would increase exponentially.”

“I sort of knew that, I guess.”

Mr. Dart leaned closer and lowered his voice a little more. “Then it might interest you to know that the prize Belinda White and Sebastian Stott are seeking is a draught from the Fountain of Youth. Funny how neither of them mentioned it. Chew on that for a minute, and see if Sebastian still strikes you as such a nice guy.”

Nate nodded thoughtfully. “Why do you care?”

By the look on his face, Nate sensed that Mr. Dart approved of the question. “I’m no magician, but magicians know me. I help keep them in line. I’ve fulfilled some important assignments, but nothing tops this. If either Belinda or Sebastian drinks that water and reverts to a younger state, it will be a really big problem. I’m not just talking about a problem for magicians, I’m talking about a problem for all humankind.”

“How do I know this isn’t a setup? You could be working for Mrs. White.”

“Before we were formally introduced, I broke my leg helping you escape Mrs. White. I shot the dwarf.”

“That was you in the car!”

“The dwarf was an Energizer. A Kinetic. He can store and release mechanical energy inside his body—jump with the force of fifty jumps, that sort of thing. He was storing up to follow you onto the roof of that antique store, so I simultaneously shot him with a rubber bullet and a crossbow. The quarrel from the crossbow struck him in the leg.” Mr. Dart smiled. “Sort of knocked him off-kilter, and he leapt into the wall. Little guy busted himself up pretty good.”

“How’d you break your leg?”

Mr. Dart studied him. He reached into a pocket of his coat and put a toothpick in his mouth. “I’ve been around long enough, my weakness is no big secret, although I’m never anxious to draw attention to it. I receive any injury that I directly inflict upon another. I punch you in the face, my nose bleeds. I break your leg, mine breaks too. I kill you . . . I die.”