"You doubt whether it is effective? Well, I can't give you any proof now; I can only say that when I was back on Mars, fooling with my first cumbersome projector, which produced only the weakest of vibrations, I blasted a big hole in the wall of my apartment, and nearly killed the Martian physician who lived in the rooms next to mine. I had a devil of a time explaining the explosion, and narrowly missed getting myself into serious trouble. In a few days I shall try to sell the weapon to the Earth Government. If they are convinced of its value, and I don't see how they can help but be convinced, our friend from the Red Planet will have to be very careful if he tries anything." Shelby glanced at his wrist watch. "Eleven thirty--my bed time," he said with mock seriousness. "But Jan, there's one favor I want to ask you before I go. Try not to see anymore of Hekalu Selba, Akar." Janice Darell made a valiant attempt to act the part of one whose pride and sense of freedom had been deeply outraged. "Mr. Shelby," she said, "what right have you to tell me what I shall or shall not do?" But a light laugh broke from her lips and spoiled her bluff. "There are two reasons," replied her companion seriously. "First, because we both believe that Hekalu Selba is dangerous; second--because I love you." He leaned closer toward her with the light of eagerness in his eyes. "Oh, I know I'm crude, Jan," he said passionately. "I'm just a clumsy engineer, not a poet or ladies' man. What I'm trying to say to you must seem awfully trite, but anyway, I want you with me always." "You mean--?" He nodded. "All right, Austin," she said quietly, looking straight into his eyes. His arms crept around her, and now he drew her gently to him. Some moments later, in the nearby pergola, the door which led to the rooms below opened, and an ancient negro clad in gaudy pajamas and bathrobe peered out into the garden. He saw the pair and recognized the girl. A happy grin came over his wrinkled black face. "Well, if dat ain't a mos' pretty sight to look at," he muttered. "My baby done come back at las', and dat sho' am a han'some boy she got dar!" He turned, and leaving the door open and the light burning on the stair, descended. Very softly and wistfully he was crooning an old darky love song. It was an hour later before Shelby's craft whirred up into the moon-bathed night over the winking lights of the city. And at the same time the big-eyed Sadu moth which had been crouching in the cypress tree, rose on its velvety wings and sped away, as though some urgent mission had suddenly claimed its attention. CHAPTER III Hekki's Proposal When Shelby reached his apartment, he immediately donned his laboratory smock and set to work. But he had scarcely finished mounting a tiny coil of wire within the hand-grip of his weapon, when the view-phone bell rang insistently.