Ganymede, the largest moon of Jupiter, was an important way station of the Solar Alliance for all spaceships traveling between the outer planets of Saturn, Uranus, Neptune, and Pluto and the inner planets of Mars, Earth, Venus, and Mercury. The colony on Ganymede was more of a supply depot than a permanent settlement, with one large uranium refinery to convert the pitchblende brought in by the prospectors of the asteroids. Refueling ships, replenishing supplies, and having a small tourist trade, it was a quiet colony, one of many spread throughout the system.

With the Solar Guard search squadrons hopelessly out of range on the other side of the asteroid belt, the cadets' only hope of saving the tiny colony lay in the beacon hidden inside the hull of the Polaris.

Leaving Wallace and half of his crew aboard the Polaris, Bull Coxine had transferred the three cadets to the Avenger and thrown them into the brig. As the ship accelerated toward the colony, Tom stared out of the small, barred viewport while Roger and Astro sprawled glumly on the hard bunks.

Roger finally broke the heavy silence. "What do you suppose Coxine meant when he said he had three passes into Ganymede?"

"Give you one guess, pal," snorted Astro.

"He obviously expects us to give him the recognition signal," said Tom.

Roger sighed. "That's what I figured. But I was hoping I was wrong."

"At least we're all immune to truth drugs," said Astro hopefully. "He won't get the recognition code out of us that way."

"That dirty space crawler wouldn't even bother with drugs," muttered Roger. "They aren't enough fun. He likes to get what he wants the hard way."

"Yes," agreed Tom. "We're in for a rough time, guys."

They all looked at each other, fully aware of what lay in score for them. Finally Astro growled, "I don't care what he does to me. I won't tell him a thing!"

"Same here!" exclaimed Roger.

Tom merely nodded, his face a grim, expressionless mask.

Suddenly three men led by Brooks, the radar operator, appeared in the passageway outside the brig. Brooks stepped forward, opened the door, and gestured with the paralo-ray gun in his hand.

"All right, you punks! Outside!"

Astro started to lunge for the pirate, but Tom grabbed him by the arm. "Take it easy, Astro. That won't get us any place."

"You can say that again," sneered Brooks. "One crazy move like that, kid, and I'll freeze you solid as a cake of ice! Now come on! Move!"

Tom, followed by Astro and Roger, walked slowly out of the brig, and guarded closely by the three pirate crewmen they were taken to the main air lock.

"All right," said Brooks. "The big ox and blondie, get in there!"

One of the crewmen opened the air-lock portal while the other two jabbed Astro and Roger with ray guns. The two cadets stumbled into the chamber and the door was slammed behind them.

"Lock it!" snarled Brooks.

When the men had secured the portal, Brooks turned and pushed Tom roughly along the passageway. A moment later they reached the control deck where Bull Coxine was hunched over his charts.

"Here he is, Captain," said Brooks. "The other two are sealed up in the air lock like sardines!"

Coxine nodded and faced Tom, a thin smile on his face. "I told you I would get the recognition signal, Corbett," he said. "And I will!" Coxine walked over to a large valve on the after bulkhead and tapped the needle indicator right beside it. Satisfied, he turned back to the cadet.

"In two hours," began Coxine, "we'll be within range of the Ganymede garrison and its radar. It takes exactly eight turns on this valve to bleed the air out of the air lock where your two buddies are. So, every fifteen minutes I'm going to ask you for the recognition signal, and every time you say no, I'll turn the valve once. By the time we get close enough to Ganymede to be picked up on their radar, you'll either have given me the signal or your buddies will be dead!"

Tom stood listening to Coxine, his blood boiling at the giant spaceman's cruelty. Suddenly he tore across the control deck and made a dive for Coxine's neck. But the big man met him coming on and with a powerful slap of his hand sent the boy sprawling back across the deck.

"You're a good man, Corbett," said Coxine, standing over the fallen cadet, "but you're a little man, and a good big man can lick a good little man any time!"

Brooks and the crewmen laughed loudly as Tom dragged himself to his feet.

"Well, do I get the signal?" demanded Coxine. "Or do your buddies get a little less air?"

Standing unsteadily on his feet, with four paralo-ray guns trained on his body, Tom thought quickly of Roger and Astro, alone in the darkness of the air lock, soon to be clawing their throats for air; of the merciless attack on the prison asteroid; of the helpless ships Coxine had looted. All these things and more flashed through the curly-haired cadet's mind as he weighed his life and the lives of his unit-mates against an attack that would devastate the small satellite of Jupiter. Tom could see through the pirate's demand for the recognition signal. Once inside the Ganymede radar screen, he could attack the Solar Guard garrison and wipe it out before it could raise a ship in defense.

"Well?" demanded Coxine, placing his huge hand on the valve.

Tom knew that if he could stall long enough, the signal aboard the Polaris might be picked up by the Solar Guard. Roger and Astro were in good physical condition. They could conserve their energy as soon as they discovered the trap. He had to stall and hope the signal would be picked up in time.

"The only thing I'll ever give you, Coxine," said Tom through clenched teeth, "is a blast of a paralo-ray!"

Coxine snarled in anger and turned the valve, shouting, "One more thing, Mister Hero! The minute the air lock is empty, you take a swim in space too!"

Tom was prepared for that. He knew the pirate would not take defeat at the hands of a Space Cadet easily. Tom was resigned to his fate. He was ready to accept anything if it would serve the purpose of ridding the solar system of Bull Coxine.

"Tie him to that chair," snarled the giant pirate captain. "And make sure he's secure, or you'll go swimming in space with him!"

Tom was shoved roughly into the copilot's chair in front of the control board and tied down with a thick rope. He winced as the heavy line dug into his arms. After inspecting the job, Coxine dismissed Brooks and the men with a curt nod and returned to his charts.

Tom sat in front of the control panel, his eyes sweeping the gauges and dials and at last fixing on the master acceleration lever. Two feet away was the lever that controlled all the power on the ship. If he could only reach it, he could stop the Avenger dead, and possibly even put the ship completely out of commission. But try as he might, he could not get his hands free.

Coxine looked up at the astral chronometer and walked over to the valve. "Well, Corbett," demanded the burly spaceman, "what's the recognition signal?"

Tom only shook his head.

"Must be pretty bad, sitting down there in the dark, hearing the oxygen feed in slower and slower. You sure you won't change your mind?"

Tom looked squarely at Coxine, hatred in his eyes, and he watched the pirate captain shrug his shoulders, turn the valve again, and return to his charts.

The young cadet watched the astral chronometer, seeing the red hand sweep the seconds away, and the black minute hand inch around the dial. Over and over, the curly-haired Space Cadet refused Coxine's demand for the recognition signal and then watched helplessly as the pirate gave the air-lock valve another twist.

Nearly two hours had passed and Tom knew that they would soon be in radar range of the Ganymede garrison. The pressure in the air lock must now be within ten units of zero. Suddenly, overhead, the audioceiver loud-speaker crackled into life.

"Attention! This is Ganymede traffic control. Identify yourself immediately with authorized code!"

Coxine glared at Tom and put his hand on the air-lock valve. "Last time, Corbett. Either you give me the Solar Guard recognition signal, or your buddies are finished!"

Tom gulped. He had no assurance that Coxine would release Roger and Astro, even if he did give him the signal. But he knew there was no choice. He looked up at Coxine.

"Do I have your word as an Earthman that nothing will happen to them?" he asked quietly.

Coxine laughed. "Sure. I'll give you my word. I'll even bring them up here so they can see the show and then let you go afterward. But by the time I'm finished with the Ganymede colony the Solar Guard will have your hides for handing out their secrets."

Tom knew what the pirate said was true. He was taking a gamble now. A gamble that by this time his signal on the Polaris had been picked up and a fleet of ships would be on their trail.

"Attention! Attention! Identify yourselves immediately!" The voice from the Ganymede traffic-control tower came over the audioceiver again. Coxine's face twisted into a half-smile.

"Well, Corbett, do I get the signal or don't I?"

"Tell them you're a Solar Guard armed freighter." Tom's voice was low. "You're assigned to operation 'Vista.'"

"Vista?" said Coxine excitedly. "Is that the code word? Vista?"

"Yes," said Tom. "Now open the valve!"

Coxine gave the valve a number of turns in the opposite direction and jumped to the teleceiver. He flipped the key open and called Wallace aboard the Polaris. "When they ask you for identification, tell them you're working on operation Vista. That's the key word. Vista!"

"Right!" answered Wallace.

Coxine then turned to the audioceiver and spoke in confident, assured tones. "Attention, Ganymede traffic control! This is armed freighter Samson, assigned on project Vista. Request clearance for approach and touchdown on Ganymede spaceport!"

"You are properly identified, Samson," replied Ganymede. "Proceed on your present course. End transmission."

"End transmission!" roared Coxine triumphantly.

The giant pirate turned back to Tom, bellowing, "Thanks, Corbett. You've just given me the key to everything I ever wanted."

"What do you mean?" asked Tom, suddenly frightened by the strange wild gleam in Coxine's eyes.

"By the time I've finished with Ganymede, I'll have every ship on their spaceport. A fleet big enough to hit any part of the Solar Alliance I want! Solar Guard or no Solar Guard!"

"No! You can't!" gasped Tom.

"Can't I?" snarled Coxine. "I'll show the Solar Guard something they never saw before. Their own ships blasting them right out of space!"

Coxine turned to the intercom, ordered Astro and Roger brought up to the control deck, and then contacted Wallace aboard the Polaris.

"Yeah?" answered the spaceman from the control deck of the rocket cruiser.

"We're going in according to plan! Train all your guns on the Solar Guard defense installations and stand by!"

"Ready any time you say the word," replied Wallace.

Jumping back to the intercom, Coxine gave orders to the power deck for full thrust, then ordered the radar bridge to relay the scanner image of Ganymede to the control deck.

As the rocket ship surged ahead under the added thrust, Tom strained against his ropes to watch the scanner and saw the clear image of the colony. He could make out the outline of the uranium plant, the atmosphere booster stations and small buildings clustered around the spaceport. As they drew closer to the tiny colony, Coxine grabbed the intercom and the teleceiver microphones and barked crisp orders to both the Avengers and the Polaris' power decks. "Full braking rockets!" roared Coxine.

Tom braced himself against the sudden reverse pressure of the powerful nose rockets, and then, in a moment, felt the Avenger come to a dead stop. Watching the scanner again, he saw that they were directly over the Solar Guard garrison. Coxine switched the teleceiver to the colony frequency and spoke sharply and confidently.

"Attention! All citizens of Ganymede colony! This is Bull Coxine. Your entire settlement is under my guns. Any attempt to raise ship and oppose me will be met with instant destruction! Every citizen is hereby ordered to assemble at the municipal spaceport within five minutes. All Solar Guard officers and men will do the same. You have five minutes to comply, or I will open fire!"

The giant spaceman flipped off the teleceiver before anyone on Ganymede could answer. Pressing with all his might, Tom managed to see more of the scanner which suddenly showed the people of Ganymede scurrying out to the spaceport in panic. Coxine watched the activity on the scanner for a second and then grunted his satisfaction.

Suddenly the hatch was thrown open and Astro and Roger were pushed into the room by two crewmen.

Coxine turned to them, smiling thinly. "You owe your lives to your buddy here. One more minute and you would've been walking with the angels. Now," he added to the crewmen, "tie them up so they can see the scanner. I want them to see how easy it is to knock off a Solar Guard garrison!"

"Why you—" Astro lunged toward the pirate but was stopped in his tracks by a blast from a paralo-ray gun behind him. The big cadet stood rigid, motionless, every nerve and muscle in his body paralyzed. Coxine sneered and turned back to the intercom while his men tied up the two cadets.

Tom and Roger looked at each other and, without speaking, knew what the other was thinking. Their only hope was the beacon signal aboard the Polaris.

After the men had tied Astro, they released him from the effects of the ray charge and threw him down beside Roger.

"How do you feel?" asked Tom.

"Like I've been run through a set of gears," mumbled Astro. "How about yourself?"

"O.K.," replied Tom. "Was it"—he paused—"was it tough in the air lock?"

Roger smiled. "Not as tough as it must have been on you up here. We realized what was going on as soon as we found out we were losing air."

The blond-haired cadet shook his head and Tom noticed that both Roger and Astro were weak from their ordeal in the chamber.

At the control panel, Coxine was bawling orders to his crew. "Jet boats one, two, three, four, and five! Stand by to blast off!"

The three cadets looked at each other helplessly.

"Russell, check in," continued the burly spaceman.

"Russell here!" replied a voice on the intercom.

"You're in charge of the party. I want you to do one thing, and one thing only! Take the largest ships on the spaceport and blast off. Don't touch anything else! Just the ships. Those you can't get off the ground, leave. We'll blast them later!"

"Aye, aye, sir."

Coxine strode over to the teleceiver. Immediately the image of a man in the uniform of a Solar Guard major appeared on the screen. His voice echoed in the control room.

"Hello, Coxine! This is Major Sommers! Come in, Coxine!"

"Yeah—" replied Coxine. "Whaddya want?" The pirate captain stepped arrogantly in front of the teleceiver's transmitting lens, and from the look on the officer's face, Tom knew he had seen Coxine on his own screen.