The waiting group fidgeted and prowled back and forth to ease their tension. Feelings of suspense began changing into gloom after two more hours had passed with no sign from the sky. Disappointed but unable to wait any longer, the technical men went back to the plant, one by one. Hank Sterling, too, and Arv Hanson finally had to leave. "Sorry, skipper," Hank muttered. "Ring us right away if it shows up." "Sure, Hank." As six o'clock went by, Chow tried to pep up his companions' drooping spirits with a simple but tasty supper, warmed up on an electric hot plate in the cabin. "What do you think, skipper? Are we out of luck?" Bud asked as they ate. "Our space friends haven't let us down yet," Tom replied. "I'm sure they won't this time." Though he didn't say so aloud, Tom was worried that their Brungarian enemies might have managed to divert and capture the energy. Mr. Swift seemed to read Tom's thoughts. "Let's hope no hitch has occurred," he said quietly. The sun went down. Twilight slowly deepened. The trees on the hillside faded from view in the gathering darkness. "_There it is!_" Bud yelled suddenly. Electrified, the four sprang up in an instant. A speck of light was sailing across the sky! But their faces fell as it drew closer. "Only an airplane," Bud grumbled. At ten o'clock Mr. Swift gave a weary yawn. "The spirit is willing but the flesh is weak," he confessed. "I got only two hours of sleep on the space wheel, and apparently last night wasn't enough to catch up. Sorry, fellows." "Why don't you go home, Dad? Hit the hay," Tom said sympathetically. Promising to take a turn on watch if the vigil continued through the next day, Mr. Swift drove off in his car. Time dragged by slowly as the three remaining watchers chatted and looked hopefully at the stars. Eventually Chow propped himself against a tree and dropped off to sleep to the accompaniment of low-droning snores. Bud too began to drowse. It was long past midnight when Tom suddenly caught sight of a moving light in the sky. He stiffened and held his breath. Another false alarm? But no! A glowing, faintly bluish mass with a comet tail of luminous orange red was slowly proceeding through the pattern of stars! "Hey, fellows! Wake up!" Tom shouted. He sprang to his feet and unlatched a single point of the star head. Within seconds, Bud and Chow were both wide awake, as excited as Tom. The blue nebulous mass moved closer and closer. The three watchers were speechless with awe. As the ball of energy descended toward them, it lit up the whole scene. The hillside looked almost as if it were on fire. The earth vibrated, and the air had the sharp smell of ozone. This was followed by a frightening clatter and rumble. The force of the energy was sweeping down rocks, gravel, and shrubbery in a hillside avalanche! "Look out!" Chow shrieked. "We'll be pulverized in this rock stampede!" He streaked for cover as a huge boulder came plunging straight toward him.