But luck was with them. Suddenly, startlingly, that green shadowy nightfall came again. "Listen!" Devries said. All was silent again in the square below. He rushed to the window and saw the throng dispersing. The Brain, on its portable platform, was moving away into one of the buildings. Apparently the Ritual was over for the day. "We'll have to work fast!" Devries exclaimed. "This side of the planet's away from Neptune now, but we don't know how long it'll last. This is our last chance!" They worked frantically, risking skinned fingers on the stone wall. About an hour later Devries tried the mutilated coin in the slot, for perhaps the twentieth time, and this time it fitted. But would it reach as far as V'Naric's key had reached? Devries wrapped his fingers carefully with strips of cloth before he tried. For a moment he thought it was useless. The metal touched nothing. Clumsily he managed to slide it forward a tiny bit more, and the silver oblong barely touched a hard surface. Instantly at the contact there came a sputter of fused metal. The silver became suddenly hot under Devries' fingers. Sparks leaped out and burnt his hand. But he didn't care. He suppressed a joyous shout as the sheet of electrical flame across the doorway ceased. They sprang through the door and stood a moment in the dim corridor, listening. Evidently their tampering had caused no other alarm. They moved swiftly to the stairs leading down into the square. Peering down through the greenish dusk, they could see one of the Proktols at the bottom of the steps, evidently on guard. Devries gestured downward, and Janus nodded silently. Those steps were solid stone, and they negotiated them silently by all Earthly standards, but they had forgotten these creatures had super-sensitive hearing. They weren't over halfway down when the Proktol sprang up, whirling to face them. Devries acted on sheer instinct. He made the remaining distance through the air in one prodigious leap. The Proktol had reached for its flame-pistol, at the same time opening its mouth to sound an alarm. But there was only a shrilling gasp as Devries' shoulder caught it in the middle and hurled it backward. Devries climbed to his feet, a little dazed. Janus took only one look at the Proktol and saw that the frail body was snapped in two; quickly he confiscated its flame-pistol. They stood quite still, listening, but there was no alarm. * * * * * In some of the radiating streets they could see the weird glow of many colored lights moving about, but the square seemed empty now in the gloom. They started to move across it, when something caught Janus' attention. He stopped.