The four stepped over to it, and McCausland tapped at the door. There was no answer at first, then from the other side there came an answering tapping--one tap, then two, then three, as though for a signal. McCausland answered in the same fashion, and after a moment the door slid back, revealing one of the strange ape men of Pluto. He saluted in a strange copy of the movement Adam had made at the time of their first contact, and McCausland, returning the salute, stepped through the door, and producing a piece of paper from his pocket began to make sketches, while the dwarf watched with interest, his face working rapidly to indicate comprehension. After a moment the captain beckoned to Reuter and both stepped down into the Plutonian room, leaving Paulette and Bjornsen on the heap of rubble at the base of the digging. The girl looked round, then in a low voice, said to the engineer: "Will you do me a favor?" "Sure. What is it?" "I'd like a souvenir. See where that part of the wall is torn? Could you break me off a little sliver of that metal to take back with me?" "Simple." The giant mechanic stepped over to the wall and twisted at a rag of metal. It tore loose with a little ping! The other two were absorbed in their pencil-and-paper conversation with the Plutonian and did not appear to notice as Paulette slipped the fragment into the pocket of her skirt. Bjornsen's eye looked along the crack and the fitting of the door, and he was shaking his head, clucking despondently. "These people," he said. "They are bad mechanics. Look at that joint. I'll fix it for them." He bent and picked up one of the atomic power drills that had been left at the foot of the dig, and applying it to the wall, turned on the power. As he did so, there was a commotion; a dozen or more of the Plutonians, all dressed in the same wrappings, but with varying numbers of metal bands, came pouring through the back door of the room. McCausland turned fiercely. "Drop that!" he shouted. "Do you want to bring them all down on us?" "I was just repairing this break for them," replied the engineer. "Don't touch anything that doesn't belong to you," replied the captain, and turning, began to draw rapidly on his paper. * * * * * The crowding Plutonians, gabbling in their guttural language, were examining the work that Bjornsen had done, gazing at him admiringly and then at the power drill he had used. Three or four of them attached themselves to him, while another picked up the machine, and pulled him along as though to lead him through the rear door of the room, while their chief made a rapid drawing for McCausland. "They want you to go with them and work for them," explained Reuter, peering over the Plutonian's shoulder as he sketched. "Just disengage their hands, gently, Bjornsen. We'll explain."