“Did you hear that?” Frank asked Joe. “Mr. Young told the reporter that the splash pad will be closed until they find the person who bubbled it up.”

  “What if they never find this Bayport Bubbler?” Joe asked, his eyes wide. “What if the splash pad is closed all summer? What will we do??”

  “We’ll do what we do best,” Frank stated. “We’ll solve another mystery, and we’ll start now.”

  “Ready when you are, Frank!” Joe said as he pulled a small book from his pocket.

  “You brought our clue book to the splash pad?” Frank asked, surprised. “What if it got all wet?”

  “That is why,” Joe said, “our clue book is protected inside a reused sandwich bag!”

  “Reused?” Frank asked. “No wonder I smell chicken salad.”

  “Tuna,” Joe corrected him. “Now let’s get to work!”

  The brothers found a bench to sit on in front of the Bayport Science Center. Between the pages of the clue book was one of Joe’s favorite pens, shaped like a hot dog with mustard. He used it to write Who’s the Bayport Bubbler? on a clean page.

  “Before we get to who,” Frank said, “Let’s figure out the other four Ws—what, where, when, and why.”

  The five Ws were questions detectives often asked while starting a case. Joe decided to start with where.

  “We already know where this soapy sudser happened—here at the splash pad,” he said, swatting some drifting bubbles away from his face. “But what could have caused it?”

  “Somebody could have poured soapy stuff down the drains,” Frank said. “If the water keeps spurting up, so would the bubbles.”

  Joe wrote Frank’s idea on the page. He looked up and asked, “But when could all that have happened, Frank? This is a busy place. Wouldn’t someone have caught the Bayport Bubbler in the act?”

  “The bubbler could have struck overnight,” Frank suggested.

  “Maybe not,” Joe said, shaking his head. “I think the Bayport Bubbler struck early this morning.”

  “How come?” Frank asked.

  “Remember when Dad worked on a case at the science center?” Joe asked. “He told us that a night guard walks the science center grounds with a flashlight until seven in the morning. That’s the time he goes home.”

  “The splash pad is here on the science center grounds,” Frank said. “The night guard would have noticed the Bayport Bubbler or the bubbles at the splash pad!”

  “Which means everything happened between seven in the morning and eight o’clock,” Joe said as he wrote 7:00 a.m.–8:00 a.m. in the clue book. “That’s when Martin said he got the call.”

  “We have a timeline. Now what about suspects?” Frank asked. “Who could be the Bayport Bubbler and why?”

  “Maybe it’s a kid who loves bubbles,” Joe suggested, “and wants to spread the fun.”

  “Or the word!” Frank said. “Lucy wanted to let everyone know about her new lemonade!”

  “Her new bubble lemonade!” Joe added. “What better way to let everyone know than with bubbles?”

  Joe began the suspect list with Lucy Lafferty. When he looked up, Frank’s head was turned toward the science center. Walking up the steps while studying an orange slip of paper was Phil.

  “There goes Phil with his top secret space formula,” Frank said. “I wish he’d let us take a look at it.”

  Joe smiled as something clicked. “Phil did give us a hint,” he said. “And also—a clue!”

  “What clue?” Frank asked.

  “The secret word,” Joe said excitedly, “was bubbles!”

  ASTRO-NOTS!

  “Phil? The Bayport Bubbler?” Frank asked, surprised. “Even if his space project has something to do with bubbles, why would he use the splash pad?”

  “I think I know, Frank,” Joe said as he added Phil’s name to the suspect list. “Phil could be sending messages to aliens on other planets!”

  “With bubbles?” Frank cried.

  “Why not?” Joe asked. “There are radio signals, light signals, even smoke signals—why not a bubble signal seen all the way from outer space?”

  “The splash pad would have to be miles and miles long to be seen in space,” Frank explained. “Like the Grand Canyon and the Great Wall of China. I learned that in school.”

  Joe looked over at the splash pad. It was pretty big, but no Grand Canyon!

  “Okay, Frank,” he agreed, “but Phil’s secret word ‘bubbles’ could still be a clue.”

  “Phil was carrying his top secret space science formula,” Frank said. “If we can read it, we’ll know if a bubbled-up splash pad was part of his project.”

  “How do we do that if Phil is in camp today?” Joe asked. “We’re not space campers.”

  “We are detectives,” Frank said, “so let’s find a way to find Phil!”

  The boys climbed the steps to the Bayport Science Center. Once inside, they were greeted by a woman behind an information desk. Her nameplate read Carolyn Novak.

  “Hi, boys,” Carolyn said cheerily. “If you’re here to visit the science center, you have to be with an adult.”

  She winked and added, “I know you’re not on a class trip, because it’s summer vacation. Lucky ducks!”

  “Um, thanks,” Frank said, “But we’re not here for the science center—”

  “Oh, then you’re here for Camp Blast Off,” Carolyn said. “You boys must know where the space suits are by now.”

  “Space suits?” Frank and Joe asked together.

  Carolyn pointed to a closed door in the near distance. “Sure,” she said with a big grin. “You’d better suit up for the Rotator Simulator.”

  “The what?” Joe murmured to Frank.

  The brothers had no clue what a “rotator simulator” was. But if it meant getting into space camp and checking out Phil’s top secret bubble formula—

  “Time to suit up,” Frank said.

  He and Joe turned toward the door. A sign read, LOCKER ROOM. CAMP BLAST OFF CAMPERS ONLY.

  “Why do we need space suits, Frank?” Joe asked as they hurried past a replica of the moon in the lobby.

  “I don’t know,” Frank admitted, “but something tells me we’re about to find out.”

  Slowly, he opened the door. Inside the room were metal lockers and about eight kids pulling white space suits over their shorts and camp T-shirts. They were so busy dressing and chatting they didn’t notice the brothers stepping inside.

  “Frank, look,” Joe whispered. “Phil is on the other side of the locker room, all suited up.”

  “Look what he’s slipping into the pocket of his space suit,” Frank whispered back. “The orange paper.”

  “You mean his top secret formula,” Joe said. “Are we lucky or what?”

  “We’ll be luckier when we get to read it,” Frank replied. Suddenly—

  “Greetings, Camp Blast Off Crew!” a voice boomed over a loudspeaker, making Joe jump. “When suit-up is complete, proceed to the loading dock. I repeat. Proceed to the loading dock in double file only.”

  The sound of a click told the brothers the announcement was over. Phil and the other campers were busy closing their lockers.

  “If this loading dock is where Phil is going, that’s where we’re going too,” Frank whispered. “But first we need space suits.”

  “How are we going to get those?” Joe asked. “We’re not campers.”

  Frank looked around for an answer. Against one wall was a clothing rack. Hanging from it were three kid-size space suits.

  “Those should fit us,” Frank said.

  “Wait, Frank—what if this Rotator Simulator is a spaceship,” Joe hissed, “and we’re blasting off to outer space?”

  “What?” Frank whispered.

  “We’d better tell Mom and Dad we won’t be home for dinner,” Joe insisted. “A lot of dinners by the time we get back from space!”

  Frank groaned under his breath and said, “This is space camp, Joe, not Cape Canaveral!”

  The brothers stepped lively toward the space suits. Most of the kids were filing out of the locker room. Phil chatted to another camper as he left the room too.

  Frank and Joe quickly slipped into the white space suits and zipped up.

  “Ready?” Frank asked.

  Joe dropped his clue book into the pocket of his space suit. “I am now!” he said with a grin. “Let’s do this!”

  The brothers high-fived and were the last to leave the locker room.

  “This is kind of cool, Frank,” Joe said as they hurried to catch up with the others. “I’m feeling like a real astronaut.”

  “Don’t forget who we really are,” Frank said. “Detectives!”

  A double line had formed in the lobby. Frank and Joe took their places behind a boy and girl. A patch on the girl’s sleeve had the name Sasha embroidered on it.

  Still curious, Joe leaned forward. “So what’s this Rotator Simulator we’re heading to?” he asked the two campers. “Some kind of virtual space game?”

  Frank groaned under his breath. What was his brother thinking, talking to other campers? He could blow their cover!

  “Huh?” Sasha asked as she turned around. When she saw Frank and Joe, she narrowed her eyes. “You’re not campers. What are you doing here?”

  The brothers traded looks. They would have to think of something—fast!

  BRACE FOR SPACE

  “Hello?” Sasha asserted. “If you’re not campers, who are you guys?”

  Joe blinked hard at the question. Then, in his best space alien voice, he said, “Greetings. We are visitors from Planet Zagon, and we come in peace!”

  “Space aliens?” Sasha asked. Then, rolling her eyes, she sighed, “Yeah, right.”

  Frank and Joe were glad to be interrupted by a voice calling out, “Good morning, space campers!”

  All eyes turned toward a tall guy standing at the front of the line. He also wore a space suit and smiled when the campers replied in perfect unison, “Good morning, Captain Trent!”

  “Captain Trent?” Joe whispered to Frank.

  “I’ll bet he’s the camp counselor,” Frank whispered. “But what is a Rotator Simulator?”

  “Something tells me we’re about to find out!” Joe said.

  “Shhh!” Sasha hissed.

  “Okay, crew!” Captain Trent went on. “Are you ready to feel what it’s like to be a real astronaut?”

  Excited voices answered at once:

  “Yeah!”

  “For sure!”

  “Bring it!”

  Joe craned his neck to see Phil at the front of the line. Wherever they were going, would he and Frank be able to check out his secret formula?

  “Okay, then, what are we waiting for, space campers?” Captain Trent boomed. “Follow me as we proceed to astronaut training.”

  Frank, Joe, and the campers trailed Captain Trent down a long hall. At the end stood double doors. Dramatically, Captain Trent opened the doors, and the kids gasped. In the middle of the room was a giant round cage with a chair inside!

  “I guess that’s the Rotator Simulator,” Frank murmured.

  “Or the biggest hamster ball I’ve ever seen!” Joe said.

  The campers gathered around the Rotator Simulator to hear Captain Trent talk. Phil was still several feet away from Frank and Joe.

  “That chair you see inside the Rotator Simulator spins upside down, sideways, even front to back!” Captain Trent explained. “It’s used by astronauts-in-training to experience tumbling-type movements in space.”

  Captain Trent further explained the Rotator Simulator while the brothers inched their way over to Phil. Joe pointed to an orange paper sticking out of Phil’s back pocket.

  “There’s the secret formula, Frank,” Joe whispered. He tilted his head to get a better look. “It’s stuffed too deep in his pocket to read anything!”

  The brothers realized they’d been noticed when Phil turned around.

  “I thought that was you guys behind me!” Phil said, surprised. “What are you doing here at space camp?”

  “Show us your science formula,” Joe said with a small smile, “and we’ll tell you.”

  “I will never show you my formula,” Phil whispered as he shoved the orange paper deeper into his pocket. “Top secret is top secret!”

  Phil stepped away from the brothers, turning his attention back to Captain Trent.

  “We’d better forget it,” Frank whispered to Joe. “No way is Phil going to spill.”

  Joe had a sinking feeling that Frank was right. Until the word “spill” gave him an idea. He motioned to Frank to follow him, then tapped Phil’s shoulder.

  Phil glanced over his shoulder and hissed, “Now what?”

  “Are you going to do it?” Joe whispered.

  “Do what?” Phil asked.

  “Go on the Rotator Simulator!” Joe said.

  “No,” Phil answered. “I don’t want to be an astronaut. I want to be an astrophysicist.”

  “You want to invent things for the space program, right?” Joe asked.

  “Right,” Phil replied.

  “What if you invented a simulator chair that didn’t just flip upside down, sideways, and back and forth—but bounced?”

  “Joe, what are you talking about?” Frank asked.

  “Some planets might have the same kind of gravity Earth has,” Joe explained. “So a bouncing spaceship might come in handy.”

  “Astronauts would need to practice on a bouncing chair!” Phil said excitedly. “And if I’m going to invent one—I’d have to try out the old one first!”

  “Exactly!” Joe said.

  “All right, campers!” Captain Trent announced. “Now that you all know how the Rotator Simulator works, who wants to take a spin?”

  “Ooh, ooh, I do!” Phil shouted as his hand shot up. “Me, Captain Trent. Pleeeease?”

  Joe smiled and whispered to Frank, “All systems go.”

  Phil hurried to the Rotator Simulator as campers chanted, “Phil-lip, Phil-lip, Phil-lip!”

  “I don’t get it, Joe,” Frank admitted. “Why did you talk Phil into flipping in that chair?”

  “If the chair flips upside down,” Joe answered, “so will Phil.”

  “And?” Frank asked.

  “And you’ll see!” Joe said with a smile.

  The brothers and campers watched while two other counselors harnessed Phil into the chair. After shutting the cage with Phil inside, Captain Trent explained to the other campers, “Because the chair doesn’t spin in one direction long enough and Phil’s stomach will stay in the center of gravity, he will not get dizzy.”

  Captain Trent then turned to Phil and asked, “Are you ready?”

  “Ready, Captain Trent!” Phil replied.

  The counselor grabbed a lever and pulled it all the way. The chair—and Phil—began to spin around and around, then upside down. That was when the secret formula dropped from Phil’s pocket.

  “It worked!” Joe whispered.

  A powerful breeze caused by the spinning chair blew the paper away. It drifted between the campers before dropping a few feet away from Frank and Joe.

  In a flash Joe darted over to the secret formula and snatched it up. Carrying it over to Frank, he declared, “One small step for me—one giant step for our case!”

  POP SECRET

  “Good thinking, Joe,” Frank said. “Let’s read the formula before Phil stops spinning!”

  The campers were still cheering for Phil while the Hardys studied the writing on the orange paper.

  “This doesn’t look like a science formula,” Joe said. “More like some shopping list!”

  Frank read the list softly out loud: “Dishwashing liquid… corn syrup… water. If it is a formula, what’s it for?”

  Joe flipped the paper over. “Phil wrote the name of his experiment,” he said. “He calls it Phil Cohen’s Unpoppable Bubble Experiment.”

  “So it is a bubble experiment!” Frank said.

  Joe wrinkled his nose in confusion. “Bubbles that don’t pop?”

  “Okay, you guys,” a voice demanded. “How did you get my formula?”

  Frank and Joe turned to see Phil. His hair was mussed up from the spin. The campers were already cheering for Sasha, the next volunteer to ride the Rotator Simulator. “Your formula dropped out of your pocket, Phil,” Frank said.

  “A breeze from the spinning chair did the rest,” Joe added. He held up Phil’s formula and asked, “So what do bubbles have to do with space?”

  “I thought you needed air to blow bubbles,” Frank said. “And there’s no air in outer space, right?”

  “Right, but there is air on the International Space Station,” Phil explained. “That big laboratory in space where astronauts work and conduct experiments.”

  “And blow bubbles?” Joe asked.

  “Making water bubbles was one of their experiments,” Phil explained. “Because there’s no gravity in the International Space Station, there’s nothing to pull a bubble down and make it pop.”

  “Cool,” Frank said.

  Phil puffed his chest out proudly. “I may not be on the International Space Station,” he said, “but with my scientific formula I will make unpoppable bubbles on Earth for the first time!”

  Joe rubbed his chin thoughtfully. “Unpoppable bubbles… I thought they sounded familiar,” he said.

  “Familiar?” Phil asked. “How?”

  “Unpoppable bubbles was Sherman Singh’s science fair exhibit at school this year,” Joe replied. “I just remembered.”

  “Are you serious?” Phil exclaimed. “I must have been too busy with my own school science fair project to notice Sherman’s.” He grabbed the orange paper, crumpled it in his hand, and muttered, “So much for top secret. More like flop secret!”

  “You can still invent the bouncing simulator chair,” Joe told Phil, “now that you tried the flippy one.”