‘The Invisible Clue’

No part of the school week is sweeter than three o’clock on Friday, particularly after a math quiz. But even after the bell rang, our substitute teacher, Mrs. Kelly, kept us in our seats.

“Nobody’s leaving until I get to the bottom of this,” she said, holding up a piece of paper with brown writing and figuring on it. “This was in the wastebasket. It looks like a cheat sheet for the quiz, written in invisible ink. Someone brought this to class while still invisible, so I wouldn’t see it, and then managed to develop it. Cheating is a serious matter, and nobody’s going to leave until I find out who did this.”

“Scotty, you have to do something,” Allison whispered to me. “Solve the case so we can go!”

“Um, Mrs. Kelly, I might be able to help,” I said. “I’m kind of the school detective.”

“Is that so?” she said, looking down at her seating chart. “You’re Scotty, right? Oh, yes, your father is the police chief, isn’t he? Like father, like son, I imagine. Very well, young man, would you like to launch an investigation?”

I don’t think she believed me about being a detective, but I nodded yes. I looked around at my classmates. No one looked particularly guilty, just eager to leave. “May I see the paper, ma’am?” I asked.

“Well, any sixth-grader who says ma’am without being told deserves my complete cooperation,” she said. “Here you are.” She handed me the paper.

It was a cheat sheet, all right, and it sure looked like developed invisible ink, which forms in an unusual brown color. But how did the culprit develop it? From what I knew of invisible ink, heat would do it. I looked around the room and zeroed in on the lamp on the teacher’s desk.

“I’m pretty sure the bulb in that lamp would give off enough heat to develop the ink,” I told Mrs. Kelly.

“But I was here the whole time,” she said. “You mean someone did this right under my nose?”

“Well, did anybody come up to the desk during the quiz to ask a question?”

“Now that you mention it, I recall three students coming up – him, him and him.” She pointed out Franklin, Carter and Ramon – but who was the cheater?

I had an idea. Like I said, I knew a little about invisible ink. (And no, I’m not a suspect!)

“I need everyone to stay real quiet,” I said.

I then walked to Ramon and leaned close to him, like I was listening for something. I stayed there a few seconds and then went over to Carter and did the same thing, and then moved on to Franklin. When I was done I stepped back to the front of the class.

“I’m sorry, Carter, but you made the cheat sheet.”

“Aw, man!” he yelled. “How’d you know?”

“How indeed?” Mrs. Kelly asked. “What were you listening for?”

“Actually, nothing,” I said. “That was just misdirection. I was really trying to smell something. See, the most common form of invisible ink is lemon juice.” I faced Carter. “Sorry, dude, but you smell like lemons.”

“Man,” he said as he moaned. “I just wanted to get a good grade on the quiz. Is that so bad?”

“Good grades come from studying, young man, not cheating,” Mrs. Kelly said. “But I am not heartless, so I will let you retake the quiz, and no tricks this time. The rest of you may go now. And Scotty, I’m giving you extra credit.”

That was good news – since I’m not that great in math!

Special thanks to Brendan Mallory for this week’s illustration.

Mike Mallory’s new book, “Sherlock Holmes: The American Years,” is coming soon. Now in bookstores: “Universal Studios Monsters: A Legacy of Horror.” For more about Mike Mallory, visit michaelmallory.com.