"I have a hunch," Tom went on, "that the fish might be repelled by the unusual scent of those s.p.a.ce plants. If so, we could scatter them among the earth plants to keep the fish away."

Mr. Swift was impressed by Tom's idea. As soon as they had returned to Enterprises, he proposed that the experiment get under way.

Tom volunteered to undertake the job at once with Bud. While the young inventor phoned his copilot, Mr. Swift went to his own laboratory to prepare the plants for shipment.

Twenty minutes later the boys took off in a jet. The plants had been parceled in transparent plastic film. Glistening with a red metallic sheen, they looked somewhat like tulips with honeycombed centers.

"Scarecrow plants to drive off fishes," Bud joked. "What will scientists think of next!"

Tom laughed, then abruptly frowned. "Hey! What's that character up to?"

he said. "Trying to buzz us?"

A sleek gray jet without markings was arrowing in on them from three o'clock. Bud flicked on the radio and barked a warning. The plane made no response. As it kept coming, Tom increased speed--then rolled, dived, and changed course, but failed to shake off their pursuer.

Bud, meanwhile, was frantically calling Enterprises and a nearby airport, but getting no response. Yet their radio was working, for a voice suddenly crackled:

"_Follow the mystery plane for a landing and you won't be harmed!_"

CHAPTER V

A HUNCH PAYS OFF

Dismayed, Tom and Bud stared at each other. Apparently the enemy ship had blanked out their radio communication to all points except the mystery plane.

"Who are you and what do you want?" Tom said into his microphone.

The voice replied crisply, "_You'll find out when the time comes!_"

Tom flicked off his mike and exchanged another worried glance with Bud.

"We seem to be in a spot, pal!"

"And how! Especially if that crate's armed!" Bud muttered. "But what are they after?"

Tom shrugged. "The s.p.a.ce plants maybe--or possibly our jet."

"Might even be _us_ they want," Bud said. "Got any tricks under your magician's hat?"

Tom's brain was already racing to figure a way out. Suddenly he snapped his fingers. "Hey! I almost forgot!" he exclaimed. "Look in the locker, Bud, and see if we have the radio set that neutralizes all interference!"

Bud's face brightened. "Now you're talking!"

The set had been perfected during Tom's _Cosmic Astronauts_ adventure, in defense against an Oriental enemy's jamming-wave generator. Bud found it in the locker, dragged it out joyfully, and plugged it into the power supply.

Meanwhile, the mystery jet had banked in a wide circle and headed west.

As Tom stalled for time, it swooped back again and the same voice came snarling over the speaker.

"_I warned you to follow us! Or would you prefer to be shot down?_"

As if to back up the threat, a burst of tracer fire grazed Tom's plane.

He hastily switched on his mike. "Okay, hold your fire! I guess we have no choice!"

The jet turned back on its westerly course, and Tom followed obediently.

Meanwhile, Bud had warmed up the other radio and contacted Enterprises.

Tom switched mikes long enough to report their position, course, and speed, adding:

"Tell Security to alert Vignall Air Force Base p.r.o.nto!"

"Roger Wilco!" the Enterprises operator responded. Even if the enemy ship detected the call, Tom knew the automatic scrambling device would prevent the message from being understood.

Minute after minute, the flight continued. "Where are they taking us?"

Bud muttered.

"Some out-of-the-way landing spot probably," Tom conjectured. "I wonder how soon those fighter boys will--"

Bud suddenly grabbed Tom's arm and pointed to starboard. "There they come, skipper!"

Three gleaming specks had just burst through a cloud bank to the north.

Closing in rapidly, they were soon visible as Air Force fighter jets, flying in V formation.

"Fighter One to unmarked jet!" came the sharp command over the radio.

"Can you read me?... You'd _better_ read me, pal! I order you to proceed to Vignall Air Base under our escort or take the consequences!"

The mystery pilot, evidently bewildered by the sudden onslaught, made a frantic effort to escape. But the fighters, with almost contemptuous ease, quickly surrounded the plane and forced him to comply with orders.

Bud whooped with laughter. "Just a sheep in wolf's clothing, eh, buster?"

Minutes later, all the planes, including Tom's, landed at the airfield.

Four sullen-faced men, their hands up, emerged from the mystery jet.

Military police with drawn automatics herded them to the commandant's office. Tom and Bud followed.

"Attempted aerial piracy, eh?" the commandant said when he heard the boys' story. Turning to the prisoners, he snapped, "Who are you, and what's the meaning of all this?"

The crew captain, a hard-looking, stockily built man of about forty-five, rasped back, "We have nothing to say."

The commandant wasted no words. "Search them," he told the MP's.

Their wallets and various other items revealed little. The crew captain was carrying a private pilot's license on which he was identified as "Jack Smith." The names of the others, as shown on identification papers of one kind or another, sounded equally false.

"Probably all forged," the commandant muttered, "but we'll check them out."

He tried again to glean something from the prisoners, but they replied with sneering evasions. The commandant reddened with anger at their stubbornness. "All right. Take them to the guardhouse," he ordered.

As the MP's marched the hijackers off, Tom asked how their case would be handled.