'Not yet, my dear Doctor,' mocked the man standing in front of the braincase. 'The death you crave will not come until I have completely tested this secret of yours.'
That mocking man who spoke, the diabolical brain-thief and murderer, was Kark Al, the little Martian!
Crane even now could not believe his eyes. How could this little wisp of a Martian have broken men's necks with his bare hands, have withstood the fire of his beams unhurt?
It seemed impossible! Yet, somehow, it had been done. Even though Crane could not comprehend the explanation, he knew that at last he looked on the man he sought.
Kark Al's eyes were cruel pinpoints behind great spectacles. 'If you have tried to deceive me,' he told the brain warningly, 'if you have not told me all your secret-'
'I have told you all. You have made the culture for yourself,' said the brain thinly. 'Kill me and release me from the torture of this horrible existence!'
Rab Crane was softly releasing the catch of the ventilator grating. He had no weapon but the club and this withered little Martian was the most resourceful and remorseless killer he had ever encountered.
He crouched in the tube, stealthily opening the grating. Then the grating came loose too suddenly and slipped from his hand, falling to the floor with a clang. Kark Al whirled-
And Rab Crane sprang! He shot out of the tube like a living projectile, propelled by a terrific effort of his hunched muscles. He landed full on the Martian just as Kark Al drew his beam-gun.
They crashed to the floor together. The Martian was cat-like in his quickness, but Crane was fighting with madness born of desperate urging, and the withered little red man was no match for the Earthman's strength.
Crane tore the gun from Kark Al's hand, broke loose from the Martian and covered him with the weapon.
'Stand still, Kark Al!' he told him. 'My beams didn't seem to hurt you last night for some reason, but I think that if I fire them into your face now, you'll die.'
Kark Al's enormous spectacles glittered at Crane in calm curiosity. 'Crane, the Earthman,' he said coolly. 'It was ingenious of you to come through the ventilator. I congratulate you.
'Yes, Crane the Earthman,' Rab Crane said savagely. 'And I'm taking this brain, and the secret it gave you for Earth!'
The brain of Doctor Alph spoke rapidly in its toneless voice:
'That secret is not for any planet, Earthman! It means doom for the rest of the Solar System if it is ever released by any planet. You must destroy it — and destroy me!'
'What is the secret?' Crane asked tensely of the square black case, his gun held steady on the coolly smiling Martian.
'It is death itself, for all organic life it touches,' the mechanical, metallic voice answered. 'A new kind of bacteriophage, a strange, semi-organic microscopic life which ordinarily preys only on bacteria! Doctor Alph developed this new species, and it preys not alone on bacteria but on all organic life, expanding with incredible rapidity as it assimilates food.
'A mere pinch of this deadly new bacteriophage culture dropped on a plant would be enough to destroy rapidly all life on that planet The culture would spread like lightning, enveloping and devouring all organic matter like a flame of death running across that world. And Kark Al has a vial of the culture in his pocket! When he stole my brain, he also stole a tube of the death culture. That vial in his pocket can sweep whole worlds clean of life!'
Crane staggered beneath the dreadful revelation.
'God in heaven!' he whispered to the Martian. 'And you would use that as a weapon of Mars, against other worlds?'
He thrust out his hand, his eyes blazing with the trembling fury he felt.
'Give me that vial!' he said.
A gun-muzzle abruptly prodded Crane's back and a low, clear voice said:
'No, that vial goes to me! Drop your gun!'
Dazedly Crane let the pistol fall from his hand. He turned slowly.
Lalla Dee, the Venusian girl, had silently entered the cabin door behind him and was covering both him and the Martian with a beam-pistol.
Her face was no longer that of a soft, pretty schoolgirl but was chiseled in lines of stern resolve.
'Lalla Dee!' cried Crane. 'What does this mean?'
'It means, Rab Crane,' she said steadily, 'that just as you work for Earth, and Kark Al for Mars, I work for Venus! Yes, I'm a member of the Venusian Secret Service. Headquarters sent me on this ship at the last minute when they learned that Doctor Alph's brain had been stolen. We had been trying to get Doctor Alph's secret for ourselves, of course, and knew that the thief would try to get away on the first ship.
'I thought at first that you had the brain, but I soon saw that you didn't, that you were on the trail of it just as Kin Nilga and myself were. So I watched you, thinking you might know enough to lead me to the person who did have it. And you've done so. When you asked about the cabins tonight, I kept watch outside them.'
She held out her hand to the smiling little Martian.
'The vial of culture, Kark Al,' she said. 'It and, that brain go back to Venus.'
'Lalla Dee, you'll have to kill me before I'll let you get the culture and the brain, to be used, perhaps, against Earth!' Rab Crane cried.
'I'm sorry, Crane, really,' she said. 'But just as you love Earth, so do I love Venus.'
'You two need not continue the useless argument,' Kark Al said. 'The culture and the brain go where it has always been destined that they should — to Mars.'
'You think you can keep them even now, with my pistol covering you?' Lalla Dee said incredulously. 'You're mad!'
Kark Al chuckled. 'Your ridiculous beam-pistols! Do you think such toys are of any use when you are fighting me, Nald Arkol?'
'Nald Arkol of Mars!' Crane's exclamation of amazement was echoed by the astonishment of the girl's widened eyes, as they both stared at the withered little red man.
For they knew that they stood face to face with the most mysterious and dreaded interplanetary spy in the whole Solar System — the head of the great Martian Secret Service, the ice-hearted super-spy whom no man had ever seen but about whom every secret service man had heard terrible legends.
The little Kark Al was glittering at them amusedly.
'I see that you, have heard of me,' he said. 'Do you still think a stupid beam-gun is enough to fight me?'
He laughed harshly.
'No. It is time to end this little comedy. Seize them, Thoh!'
In answer to his shrill order there rose suddenly out of the wooden crate beside the table, a squat, horrible figure. It was human in shape and wore grotesquely the clothes of a man. But it was not human. It was a metal robot! A mechanical man!
The robot sprang toward Rab Crane and the Venusian girl. Lalla Dee fired at it. The beams hit the robot squarely, splashed off. It was made of some rare metal impervious to ordinary atomic beams. In the next instant it had seized Rab Crane and the girl, was holding them helpless in its huge metal arms.
'Now you know how the men in Doctor Alph's house were killed,' Kark Al exclaimed triumphantly. 'Also Kin Nilga, the Saturnian spy who had learned I had the brain and whom I had to kill for that reason. This robot, Thoh, whom I smuggled aboard as machinery samples, can be operated by direct order or remote control.
'And now he and I and the brain — and you two prisoners, also — are going to leave the Vulcan! A Martian naval cruiser has been secretly trailing this liner, waiting to pick me up when I leave the ship. I'm leaving now and taking you two with me. If I left you here dead, someone might read from your brains the nature of our new secret weapon. Aboard the cruiser, I'll torture valuable information from you, then destroy you completely. And then-'
The eyes of Kark Al expanded in blazing emotion that held the helpless man and girl paralyzed.
'Then the deadly culture and the secret of Doctor Alph will go to Mars. And some day ships of Mars will go forth and drop a death vial like this one on each of the other planets! We'll sweep all the rest of the Solar System clean of life. Then our people can go forth and take every world from Mercury to Pluto for ourselves. Everything — all the Universe for Mars!'
Rab Crane struggled wildly in the robot's inflexible grasp.
