And then it happened. A blasting, thundering roar echoed across the plain! Dazed, I saw the windows of the administration building give forth a blinding flash, lighting up the ice like a magnesium flare! A sound of shattering glass, of splintering plastic reached us. The administration building was being wrecked systematically by a mystic, unknown force!
With the explosion, the space-rats whirled toward it, instinctively. At the same instant my father plunged forward, Taon at his heels. The huge Jovian seized two of the men, crashed their heads together with a sickening crack. Limp, they fell to the ground, and Taon passed on. While the giant was thus disposing of two of our adversaries, my father had leaped upon another, borne him to the ground in a wild tangle of arms and legs.
All this in a split second, before I could collect my wits. The three remaining space-rats leaped back, gripping their guns. A flash of blue flame leaped out, scorching Taon's shoulder, but before the man could fire again the Jovian's huge fist had stretched him upon the ice. Moving forward, I saw the Venusian half-breed aim at my father who was still struggling with his first opponent. With all the force at my command I hurtled forward, deflecting his arm so that the dazzling blue bolt of flame tore up the ice, harmlessly. As I struggled with the man I saw Taon pick up his third opponent, hurl the inert form at the remaining space-rat, sending him to the ground. Then my father arose from the unconscious figure of his antagonist, dug a flame-gun into the half-breed's ribs. At once his struggles ceased; he raised his hands submissively over his head.
"Thanks, Stephen," my father drawled. "I shouldn't be here if you hadn't deflected his aim. How badly are you hurt, Taon?"
"Little burn," the Jovian rumbled. "No hurt much." He grinned as Clare ran toward us. "No die now, missy."
"Chin up," my father said, patting her shoulder. "It's all right now, child. Let's go back to the house."
As soon as our prisoners were disarmed and bound, we returned to the administration building. It was wrecked by the explosion. Doors and windows blown out, walls blackened. Inside, it was even worse. Chairs, desks, splintered, the floor littered with débris—and Uncle John, a charred and terrible figure, sprawled before the safe, one hand still clutching an ingot of palladium.
"What ... what was it?" I whispered. "What caused the explosion?"
"Hydrogen," my father said gravely. "As I stood there with my hands behind my back, I opened the hydrogen valve of that oxy-hydrogen blow torch. We'd used a good bit of it to blast open the safe, but there was still plenty, under that pressure, to fill the room, unite with the oxygen already present. A gas explosion, and a powerful one."
"But," I demanded, "what caused the gases to unite? What ignited them?"