Smoky turned around to look. “I've no idea. Matter of fact, I've never seen him before.”
The man obviously realized that the boys had noticed him, and instead of following them farther, he entered a door with the sign OFFICIAL PERSONNEL ONLY.
“He must be on the staff here,” Smoky went on. “Would you like to see the reactor I'm working on? The interior is hot enough to handle uranium.”
They walked over to the instrument. “We can't see the interior,” Joe pointed out.
“That's because it's running,” Smoky said. “Just follow me, and you'll find out what's in there.” He led the way to a diagram on the wall representing a slice through the reactor from top to bottom.
“This is how the machine is put together,” the student explained. “The core in the center marked A is where the uranium goes. The letter B stands for the pressure vessel, and C is the casing. These tubes extending from the core to the top are the fuelâ”
A loud sputtering noise broke out. Red sparks fiashed through the air around them. Chet turned pale and shouted, “The reactor's going to explode!”
CHAPTER IV
A Strange Disappearance
CHET dived to the floor, crawled under a workbench, turned around on his hands and knees, and stared at the other three. Frank, Joe, and Smoky remained standing.
“You guys want to get blown up?” Chet quavered.
“False alarm, Chet,” Smoky said.
“How do you know?” Chet demanded.
“Because that wasn't the atomic reactor,” Smoky explained. “It has a failsafe protection. If anything goes wrong, the motor shuts off automatically. And besides, this is a modified reactor. It doesn't have enough power for an atomic explosion.”
A man in overalls came over. He was wearing a plastic eyeshield and carrying a blowtorch. “Sorry about that,” he apologized. “I'm working on a wire coil with this torch. The coil's too soft for the flame, and that's the reason for the noise and sparks.”
“That's okay,” Smoky said. “Don't worry about it.”
As the man walked off again, Chet crawled out from under the workbench and got to his feet. He looked embarrassed. “Guess I overreacted,” he said sheepishly.
Frank soothed his feelings. “It's better than taking chances. Well, we've seen the lab. Let's report to Professor Young and find out about our assignment.”
The Bayport youths left Smoky Rinaldo tinkering with the heat shields on the atomic reactor. They rejoined the professor, who shuffled some papers, placed them on the desk, and leaned back in his swivel chair.
“How do you like the Aerospace Lab?” he inquired genially.
“We like it fine, Professor,” Frank declared, “except for one thing.”
“What's that?”
“We were being followed.” Frank told him about the man who seemed to be shadowing them through the lab.
Young frowned. “I've never seen anyone who matches that description, but I'll try to find out who he is. The lab is strictly off limits to unauthorized personnel.”
He ordered through the intercom an immediate search of the premises. Then he turned back to his visitors. “Now,” he said, “let me tell you about the mystery.”
The boys leaned forward in their chairs, eager to hear every word.
“It concerns Dr. Adrian Jenson,” Young went on. “You may have heard of him.”
“The rocket scientist,” Joe said. “He's been working on space probes ever since the astronauts landed on the moon.”
“And he won a prize for his math on trajectories,” Frank added. “The path of reentry from outer space into the earth's atmosphere.”
Young smiled. “You know your rocketry,” he complimented them. “Well, Dr. Jenson and I have been working on a revolutionary new engine powered by nuclear energy. We call it the Firebird, and it's due for a test flight in a couple of weeks. Dr. Jenson flew to Australia three days ago to follow the flight of the Firebird at the Woomera Monitoring Station.”
“Australia?” Chet spoke up. “Why there?”
“When a rocket is fired into orbit from our Space Flight Center, its path over the Southern Hemisphere is followed at tracking stations south of the equator. Woomera is one of the best of these installations. We are cooperating closely with the Australian government in monitoring our missiles, and our people go there frequently.”
“But why the mystery?” Joe asked.
“Dr. Jenson never got to Woomera. He hasn't been heard of since he left Princeton!”
Frank let out a low whistle. “Did he actually get on the plane?”
“Yes. We checked with the airlines. He arrived in Sydney and picked up his luggage. There the trail ends. We also searched his desk for clues, but found nothing.”
“And you've notified the Australian police?” Joe asked.
“We did that immediately and they've been working on it ever since. However, both we and NASA wanted a top-flight investigator assigned to the case at this endâespecially since there were indications that the plotters had been after him in this country. Our project's top-secret, so the investigation has had to be kept under wraps, and your father seems the ideal man to handle it. But so far we have no real clue to Dr. Jenson's whereabouts.”
“Maybe enemy agents kidnapped him!” Chet exploded. “Maybe they're brainwashing him!”
“That's possible,” Young admitted. “The Firebird Rocket is classified. Dr. Jenson and I are the only scientists who know the secret of the nuclear engine. If enemy agents kidnapped him, he may have revealed the secret. A foreign power could be building a Firebird right now!”
Frank said, “You mentioned that someone had been after Dr. Jenson in this country.”
Professor Young nodded. “A neighbor noticed a car with Florida plates parked outside his house after he left. And the police discovered that his home had been broken into and ransacked. Also, telephone company records show that a call was made from there that same night to a pay phone in Florida near the Space Flight Center.”
“So that's why Dad's been concentrating on the case down in Florida!” Joe said.
“Exactly. But he wanted all aspects of the case covered and decided his sons could handle the investigation here at the Aerospace Lab. So here you are.”
“And we've brought Chet,” Frank said. “He's helped us many times before and is reliable.”
“That's fine,” Young said. “I trust your judgment.”
Chet grinned and said he would do his best to help the Hardys crack the case.
The professor continued. “Your task is to investigate all possible leads at the lab and see if you can find the clue you need to solve the mystery while your father does the same at the Space Flight Center. I have some information that might help you.”
“Oh?” Frank asked. “What is it?”
Young's answer surprised him. “Jenson and I received a warning letter and threatening phone calls. Here, I'll show you.”
He reached into a drawer and took out an envelope. Removing the letter, he handed it to Frank. Joe and Chet craned their necks to see it. The message was crudely pieced together from words out of a newspaper.
It said: Kill the Firebird or else!
“Someone's trying to sabotage your rocket!” Joe exclaimed. “They don't want it to be launched.”
“That's right, and whoever wrote the letter means business.”
“Professor,” Frank said, “do you realize that you may be in great danger yourself?”
“Everyone here is aware of that. I have been assigned a personal bodyguard, without whom I do not leave the building. I don't want you to worry about me. Just find Dr. Jenson!”
Frank was about to say something when he heard a noise outside the door.
“An eavesdropper!” Frank thought. Leaping out of his chair, he strode to the door and swung it wide open.
Smoky Rinaldo was standing there!
“Hi,” Frank said. “Are you interested in our conference?”
Smoky looked surprised. “I didn't know a conference was going on in Professor Young's office. When I heard voices, I stopped momentarily to see if I should come in or not.” Glancing past Frank, he addressed Young. “I can't tell if the fuel is getting hot enough. Would you mind checking it when you have a chance?”
“I'll be right along, Smoky,” the professor promised. Then he said to the boys, “I'll phone the Nassau Club and make arrangements for you to stay there while you're in Princeton. It's on Mercer Street.”
Young made the reservations, then went with Smoky to the atomic reactor while Frank, Joe, and Chet drove to the Nassau Club. The driveway curved in a semicircle past the steps leading up to the front door of the stately building.
Frank parked the car. “Do you think Smoky was eavesdropping?” he asked as the boys got out.
“I'm inclined to think he's honest,” Joe said. “But we'll keep an eye on him.”
The boys entered the building and went to the front office to see about their room. Frank inquired while Joe and Chet looked around.
A hallway led through the first floor to a coatroom at the rear. Members of the club were seated in the reading room to the left, scanning the latest newspapers and magazines. Two portraits hung on the opposite wall, flanking the entrance to the main dining room.
“I wonder who those old geezers are,” Chet whispered to Joe.
The younger Hardy walked closer, surveyed the inscriptions under the portraits, and came back. “They're two presidents of the United States,” he said. “Woodrow Wilson and Grover Cleveland.”
Frank strode out of the office and announced that they were set for the night. The three drove to the rear of the club and left the car in the parking lot. Walking toward the back door, they examined the building, which had plenty of corners and angles, tilting roofs and high eaves.
“The club would make a good haunted house,” Joe suggested. “All we need is a spooky face at the window. Frank! There he is!”
“Who?” Frank asked, glancing in the direction his brother had indicated.
“The guy from the lab!” Joe gasped. “He was right there, looking out that window. The fellow with the tinted glasses!”
“I don't see him now,” Frank stated, “but let's go inside and see if we can catch him!”
The boys hurried up the wooden steps and through the coatroom door. Seeing nobody, they hastened down the hallway into the reading room, through the dining room, and to the front door.
A footfall on the carpet made them whirl. Their shadow was trying to tiptoe down the stairs to the basement!
The boys rushed after him. As they reached the bottom of the stairs, they saw him run into the bar. By the time they got there, he was exiting by another door.
The pursuers went pell-mell up the stairs to the first floor, and then to the second floor, where Chet was too exhausted to go any farther. He sat on the top step and watched the Hardys race along the corridor to where the man was climbing out the window. The fugitive slid down the fire escape to an alley at the bottom, and hurried around the corner into Nassau Street.
When Frank and Joe reached the spot, the man had vanished!
CHAPTER V
Night Visitor
“No SIGN of him,” Joe said, looking up and down the street. “He could be anywhere by now.”
Frank nodded glumly. “You're right. We lost him.”
The boys returned to the club and picked up Chet, then went to their room. It overlooked the alley and had a fire escape under the window.
“Good,” Chet declared when he noticed the exit. “We can get out of here in a hurry if we're cornered by crooks. Say, how about chow? I haven't eaten since breakfast. I might faint.”
“If you do, you'll shake up the club,” Joe quipped. “It wasn't built for your weight.”
Chet looked pained, but Frank came to his rescue. “I'm with you, Chet. It's dinnertime anyway.”
The boys freshened up a bit, then went to the dining room. After giving the waiter their order, Chet leaned back in his chair. “Well, Hardys,” he grinned, “do you have a plan for solving the big mystery yet?”
“We're working on it,” Joe said, sipping water from his glass.
“I think Jenson was kidnapped by a foreign power,” Chet declared.
“Maybe he
worked
for a foreign power and left on his own,” Joe put in.
“You mean as a spy?” Chet asked.
Joe nodded. “Perhaps he developed the Firebird Rocket and sold the secret to someone else.”
Frank shook his head. “But why would he wait until the United States finished building the missile ? I think he would have given away the secret earlier and stolen the plans in order to prevent us from completing the project.”
Chet nodded. “I'm with Frank. The spy angle doesn't seem to fit in this case. Jenson was probably kidnapped.”
“So where do we start with our work?” Joe wanted to know.
“We interview all the people at the lab,” Frank said. “Let's hope somebody there will be able to give us a line on that bearded creep.”
The boys discussed their strategy during dinner, and after they had dessert, Chet suggested that they go for a walk to clear their heads.
“I have a better idea,” Joe said. “I noticed a sign saying that there's dancing after dinner. Why don't we listen to the music for a while?”
“Oh, good,” Chet said. “I'm all for it.”
A combo was playing in the lounge, and couples edged onto the dance floor. The boys sat down and before long Joe noticed three attractive girls standing nearby.