“I’ll just use my gym clothes,” Chet said.

  Dr. Green turned to Frank and Joe. “Let me know if you need any help with anything, boys,” she said, handing them the hall passes. “I’m going to do my own investigating. Hopefully together we’ll figure this one out.”

  “We’re on the case,” Frank said. He and Joe were known for solving mysteries around Bayport. When the school time capsule had been stolen last year, Frank and Joe had been the ones who’d found it. They’d helped their neighbors and friends find missing watches and jewelry, and they’d even turned up a few lost dogs along the way. Dr. Green often asked for their help when something went wrong.

  “Glad to hear it. I’m going to call one of the janitors to clean up the mess.” Dr. Green took off to find help, and then turned back to head toward the main office. When she was gone, Joe pulled his notepad from his back pocket and looked at Chet.

  “Let’s get to work, then,” Joe said. He started to scribble Who, What, When, Where, Why, and How down on the page, as they made their way back to the gym. They always started with those six words when they were investigating a mystery. Their father had taught them that asking these questions helped them see the case from all different sides. Sometimes it turned up clues they hadn’t even realized were there.

  “What and Where—those are easy,” Frank said. “A sliming in the gymnasium.”

  “A sliming?” Chet said, his eyes wide. “Isn’t there a better way to say it?”

  “That is what happened,” Joe said, and shrugged. “But we can call it a prank. I’m still not sure that’s what it was, though.” He wrote down Prank? under “What,” then Gym under “Where.”

  “When—that’s another easy one,” Chet said. “This morning at around eight thirty a.m.”

  Frank was staring at the ceiling, studying the bucket that was still there, perched on one of the rafters. It looked like it was hooked up to some kind of electronic device, like it was automatic. “There’s no strings or anything,” he said. “Someone must have used a remote. They must’ve put it there before the assembly, maybe even before anyone came into school . . .”

  “But why?” Joe asked. He tapped his pen on his notepad, looking at that word. “To ruin Chet’s chances at becoming president? Or was it something more harmless? Did they just want to make a joke?”

  “A joke!” Chet exclaimed. “Whoever did it must hate me. It was so embarrassing.”

  “Who wouldn’t want you to win? Who would have a motive?” Frank asked. They used that word, “motive,” a lot. It just meant why a person would want to do something. It was like describing someone’s reason for stealing something, or playing a prank, or lying.

  “There’s the obvious answer,” Joe said. He walked over to the first row and sat down. “Cissy wouldn’t want Chet to win the election, because that would mean she’d lost for the first time ever at anything. But do you think Cissy would do something like that? Or Phil? He was helping her campaign, but still . . .”

  Joe looked around at his friends. They all started laughing—even Chet. “No, definitely not,” Chet said. “I don’t think Cissy would do that.”

  “She’s so honest!” Frank laughed. “Remember that time she found a hundred-dollar bill at the school carnival? She went around to everyone until she found out it belonged to Phil’s grandfather. She could’ve just kept it, but she would never.”

  “Besides,” Chet said, “Cissy’s one of my good friends. Phil, too. I don’t think they’d ever do that to me.”

  “I don’t think so either,” Joe said. He didn’t even bother writing Cissy’s or Phil’s name down on the list. He wrote Didn’t want Chet to win under “Why,” but then he also wrote Prank. “Is there anyone you don’t get along with? Anyone you can think of who would do that?”

  Chet shrugged. “Not really.”

  “I don’t know anyone who doesn’t like you,” Frank said. It was true. Chet was one of the friendliest guys at school. Everyone was always saying how nice and funny he was. That was one of the reasons Frank and Joe had wanted him to run for class president in the first place. They knew he had a real chance.

  Chet picked some of the dried slime from the back of his hair. “Well . . . ,” he said, thinking. “Maybe there’s one person.”

  “Who?” Joe asked. He brought his pen up, getting ready to write.

  Chet sat down on one of the folding chairs beside Joe. “Rubin.”

  “Rubin Kratz?” Frank asked. Rubin was one of the biggest kids in the fourth-grade class. Everyone said he was going to grow up to be a really good athlete.

  “Yeah, he’s my lab partner,” Chet said. “Something I did must’ve annoyed him. He kept making fun of me for running for president.”

  “Did you see him at the assembly?” Frank asked.

  “No,” Chet said. “I was looking for him, but he never showed up.”

  Joe wrote Rubin’s name down under “Who” and smiled. Maybe it was only one suspect, but it was a start. “Let’s go, then,” he said, standing up. “I want to talk to Rubin.”

  5

  On the Case

  Chet stood but didn’t follow them. He looked down at his stained shirt and pants. He had tucked the tie into his pocket, and the end of it was hanging out, still covered in green slime. “You guys should go,” he said. “I can’t go out there like this. I’ll change into my gym clothes and try to wash the rest of this goo out of my hair.”

  He stared at his sneakers as he said it. Frank glanced sideways at his brother and frowned. Chet had seemed better when they’d been asking him questions, but now he was upset again—it was obvious. “Don’t worry,” Frank said. “We’ll find out who did this. Everything will be back to normal tomorrow, and you’ll give one of the best speeches in Bayport history. No pranks and no slime.”

  “I hope,” Chet said, before walking toward the locker rooms.

  When the door shut behind him, Joe shook his head. “I feel so bad for Chet,” he said. “He’s really upset.”

  “I know,” Frank said as he headed out the gym doors. They walked down the hall, past the cafeteria. Some kids were already going to their next class. A group of girls in front of them was laughing. Frank thought he overheard them whispering something about a prank, and slime, but he tried to ignore it.

  “Do you really think Rubin would do something like that?” Joe asked. “He’s kind of mean, but is he really mean enough to play a prank on Chet in front of the entire school?”

  “I guess we’ll find out,” Frank said. He scanned the hallway, looking for any signs of Rubin. He was hard to miss. He was at least a foot taller than everyone else.

  As they walked past the principal’s office, Dr. Green peeked her head out of the door. “Frank! Joe!” she called. “Any luck so far?”

  “Not yet,” Joe said. “But we have a few leads.”

  Leads were the different people or places that the boys were going to investigate. Leads weren’t as official as clues, but they were always a good place to start. Chet had given them the lead about Rubin, and now they would follow it and see what happened.

  Dr. Green rubbed her hand across her forehead. “I wish I had more to tell you,” she said. “I just held a teachers’ meeting, but nobody saw anything strange. Whoever set up the prank must have done it early this morning, or maybe even yesterday when no one was looking.”

  Frank was about to tell her about the bucket, and how he thought the person must’ve used a remote, but just then a tall blond boy walked past. “Is that . . . ,” Frank started.

  “Rubin,” Joe whispered. He grabbed his brother’s arm and pulled him down the hall. “We have to go, Dr. Green!” he called out. “We might have something! But we gotta run!”

  They didn’t wait to hear Dr. Green’s reply. A group of second graders was going out for recess and the halls were crowded now. The Hardys could see Rubin twenty feet ahead of them. He was walking alone through the fifth-grade wing.

  The boys stayed close behind Rubin as he got to the end of the hall. Just when he was about to go down the stairs, Joe called out to him, “Hey, Rubin! Can we talk to you?”

  Rubin turned around, looking at Frank and Joe, his blue eyes wide. They had never seen him seem scared before now. Rubin stood at the edge of the stairs for a moment, and then, without saying a word, he ran down them.

  “What was that about?” Frank asked. “Why would he run away like that?”

  “He must be hiding something,” Joe said.

  They didn’t wait another second. They took off toward the end of the hall, running after him.

  6

  The One That Got Away

  By the time they got downstairs to the music wing, Rubin was already gone. There was a group of students waiting outside the band room, their instrument cases in their hands.

  “Where did he go?” Frank asked, looking down to the end of the hall.

  “It’s like he disappeared,” Joe said. He walked over to a boy with braces and freckles. The boy was holding a saxophone case. “Did you see a tall kid run past? Blond hair?”

  “Yeah. He went down there,” the boy said, pointing to a room two doors away. “The orchestra room, I think.”

  Frank and Joe thanked the boy, went two doors down, and opened the door just a crack. There were about fifty chairs set up with music stands. All of them were empty. Rubin wasn’t there.

  Joe put his finger over his lips as a signal to Frank to be quiet as they snuck inside. Why was Rubin hiding from them? It seemed like proof that he’d done something wrong. Most students at Bayport knew that Frank and Joe were detectives who had solved many cases before.

  “You go that way,” Joe whispered, pointing to the side of the classroom with two pianos. “I’ll check the closet.”

  Joe crept along the wall, being as quiet as he could. He’d been in the orchestra room only a few times before, mostly to visit his friend Callie. She sometimes liked to use lunch to practice her violin. He knew everyone kept their instruments in the closet. It seemed like the perfect place for someone to hide.

  When he got to the closet door, he threw it open, turning on the light. There was a long row of black cases of all shapes and sizes. Rubin wasn’t there. Joe was just about to turn around when he saw something move in the back corner. It looked like one of the cellos was swaying side to side.

  “Rubin, I can see you!” Joe called. He turned back, waving for Frank to come over. “We know about the assembly today,” Joe went on.

  Rubin peered out from behind the giant cello case. “Please don’t tell Dr. Green,” he pleaded. “I already have three detentions. My dad’s gonna be so mad at me.”

  Frank ran up behind Joe and stared into the narrow room. Rubin looked like he might cry at any moment. He sat against the wall and held his head in his hands. Normally Frank would feel bad for him, but he couldn’t stop thinking about what Rubin had done to Chet. Chet didn’t deserve to be made fun of like that or have his speech ruined.

  “Dr. Green asked us to find out who did it,” Frank explained. “We have to tell her. Besides, Chet is one of our best friends. Why would you play a prank on him in front of the whole school? Were you trying to ruin his campaign?”

  Rubin looked up, his brows drawing together. “What are you talking about?”

  “The bucket you put above the stage,” Joe said. “As soon as Chet went up there to give his speech, you poured the slime down on him.”

  Rubin shook his head. “The slime? I wasn’t even at the assembly this morning!”

  Frank was confused. “Then what are you talking about?”

  “I thought you knew that I skipped the assembly. I thought that was what you were talking about. I hate school elections. They’re stupid,” Rubin said.

  “If you weren’t in the gym this morning, then where were you?” Joe asked.

  “I was outside, behind the playground. Adam and I play cards there sometimes. That game—Spit.”

  Frank knew the game. He and Joe played it sometimes, usually when they went camping and they had only a deck of cards to keep busy with. “So you don’t even know about the prank?”

  Rubin shrugged. “What prank? I really don’t have a clue what you’re talking about.”

  Just then Frank heard a noise behind them.

  “Rubin, you in here?”

  Adam Ackerman came into the orchestra room. He was one of the biggest bullies in Bayport. He was always trying to get someone to give him their seat on the bus, or making one of the third graders buy him ice cream at lunch.

  Rubin peered out of the closet door and waved at Adam. “Yeah, I’m here,” he said. “I was just leaving, though.”

  “Are these dweebs bothering you?” Adam asked. He narrowed his eyes at Frank and Joe.

  Frank ignored him. He’d known Adam since kindergarten—he was used to Adam calling them names. “Were you at the assembly this morning?” Frank asked Adam.

  “Uh . . .” Adam looked behind Frank, at Rubin.

  “Just tell them the truth. It’s okay,” Rubin said. “They don’t care if we skipped it. They’re trying to find out something about a prank.”

  Adam sighed. “We were out behind the playground, playing a card game. I beat Rubin for the third time this week.”

  Joe nodded, knowing what that meant. Rubin had an alibi, proof that he was somewhere else when the prank happened. There was no way he could’ve set off the bucket from all the way on the other side of the school, outside, and behind the playground. It didn’t matter if he liked Chet or not. He wasn’t their suspect.

  “Thanks, guys,” Frank said as he headed toward the door. “We can check this off our list.”

  Joe followed behind him. When they were almost outside, Rubin called out to them. “Wait—you promise you won’t tell on us?”

  Frank shook his head. “Don’t worry about it,” he said. “That’s not what we’re interested in.”

  They slipped out the door and started down the hall. They should’ve felt better about what had just happened. They’d been able to cross Rubin off their list of suspects. The problem was that there had been only one person on that list . . . and now there were none.

  “What are we going to do now?” Joe asked as they climbed the stairs. “If Rubin didn’t do it, then who did?”

  7

  The Evidence

  Frank and Joe stood at the back of the gym, looking at the bucket above the stage. They’d decided to do what they always did when an investigation seemed to hit a dead end. . . . They’d gone back to the scene to take a second look.

  “There has to be something we missed,” Frank said, scanning the stage. He wasn’t sure what he was looking for exactly, but he hoped there was some sort of clue the “slimer” had left behind. In their other cases suspects always left something behind!

  The room was empty except for the janitor, Mr. Miles, who was folding up the chairs one by one. There was a ladder on the stage, just below where the bucket was still resting.

  Frank and Joe walked down the aisle and checked behind the podium, where Chet had stood. The slime had been mopped up, and the microphone had been wiped clean. Frank crawled under the stage, but there was nothing there either.

  “Mr. Miles?” Joe said, turning to the white-haired man behind them. “Do you think we can get that bucket down? We’re looking for clues.”

  Frank went to climb the ladder, but Mr. Miles waved him away. “Let me get it for you—that’s too high for you to climb up.”

  Mr. Miles climbed all the way to the top while Frank and Joe held the bottom of the ladder for him. When he came back down, he handed them the bucket. “There you go,” he said. “It was sitting on one of the rafters. Has a motor in it. . . . See here?”

  He pointed to the bottom of the bucket, which had a hole in it. There was a thick plastic trapdoor. “You were right, Frank,” Joe said. “Someone must’ve had a remote. When they hit a button, the trapdoor opened up and the slime fell down on Chet.”

  “Now, why on earth would anyone do that?” Mr. Miles shook his head. “Kids are crazy these days.”

  Frank turned the bucket over, and some extra slime came out, turning his hands green. “Yuck.”

  “What time did you come in this morning?” Joe asked, looking at Mr. Miles. “Did you see anything strange? Did you notice the bucket there?”

  Mr. Miles straightened up. He had a large, bushy white beard that made him look a little like Santa Claus. “I get here every morning at six a.m. I went through here this morning around seven thirty, just before school started, because we keep some brooms in that closet over there.” He pointed to the corner by the locker rooms. “But I didn’t see the bucket. This ladder was out, and I thought that was strange. But sometimes the other guys on my staff move it. I don’t know.”

  “So the ladder was out? By the stage?” Frank asked.

  Mr. Miles pointed to the corner. “It was folded up over there. But it’s normally in the closet.”

  “Did you notice anyone here who wasn’t supposed to be? Any kids who came in early?”

  Mr. Miles shook his head. “Nothing odd . . . no one I can remember. But now that you mention it, I did see something weird just before you got here, when I was cleaning up that mess.”

  He walked over to the garbage can in the corner and pointed into it. “What do you suppose those are?” he asked. “They looked strange to me. Might be connected to your prank.”

  Frank and Joe leaned closer. There wasn’t much in the trash can except a couple of plastic jars on the bottom. The insides were coated with green slime. Frank reached in and plucked one out, studying it.

  “Gross,” Joe said, scrunching his nose up. “That had to have been what fell on Chet.”

  Frank flipped the plastic jar over. There was a small white tag on the bottom. “Look, a clue!” he said, squinting to read it. “Three dollars and ninety-nine cents. Crazy Eddie’s.”