Ro called to Na and Carlson and stepped into the clearing. Grimm advanced a few steps, still smiling. Then his expression changed to one of fearful surprise. His eyes were fixed on a spot to Ro's right. Ro followed his glance. He saw three rat men standing some thirty feet away. They were half hidden by foliage, but Ro could see that one carried a ray gun. He was sighting along the barrel, aiming at Grimm. Ro drew back the stone in his hand. He knew in that instant, his throw would be too late. Grimm threw up his arms instinctively to ward off the burning death he expected. But the rat man never fired. A lance of flame seared past Ro from behind him. The rat man holding the gun screamed in pain as the charge burned into his chest. He fell forward. Ro released the rock in his hand, but it went wild. The remaining rat men fled. Ro turned to find Carlson holding a smoking gun. "Lucky I happened to pick this up back there," the Earthman said. "Very lucky," said Ro. "For Grimm's sake." "Into the sphere," Grimm called. "Those other two will be bringing the whole tribe back." Carlson retrieved the dead rat man's ray gun. Ro ushered Na across the clearing to the door of the sphere. Na hesitated a bit, then entered reluctantly. Ro followed, then Grimm and finally Carlson. "I guess I owe my life to you," Grimm said, as Carlson closed the door. "And I owe you an apology for the way I acted this morning. I didn't understand how it was between you and Charlotte. She explained. It was quite a shock, but I guess I'll live. Apology accepted?" He extended his hand. Carlson took it sheepishly. "Tell me," Ro interrupted, "did you meet any rat men when you took the sphere?" Grimm shook his head. "Those three just now are the first we've seen since we left you. When we got here the place was deserted. We--" A cry from another section of the sphere made them turn. It was the professor's voice. "Here they come," he shouted. "Hundreds of them." * * * * * Carlson and Grimm dashed through a doorway in the direction of the cry. Ro followed, entering a spacious room. He was taken back by the intricate machinery he saw. There were countless numbers of dials and levers, gauges and indicators. Carlson and Grimm took their places at tiny portholes. Ro found an unoccupied post and peered out. He saw a mass of grey bodies charging toward the sphere. There were more rat men than he'd ever seen at one time before. They seemed to be climbing over one another as they raced from the forest. A sudden whirring of machinery within the sphere caused Ro to turn from the porthole. The three Earthmen were working levers and twisting dials frantically. Additional portholes appeared in the sides of the sphere. Long tubes rose on folding legs from the floor and slid through the openings. "Take aim," the professor shouted in a commanding voice.