"Guess you and I had better get some shut-eye too, pal," Tom told Bud. "And I think I won't tell Dad until morning." [Illustration (Tom, Bud and Chow celebrate building Exman)] The two boys decided to bunk on cots in the small apartment adjoining Tom's laboratory. Exman, meanwhile, was left locked in the laboratory with a tiny "night light" showing on him. "Just a little ray of energy to keep him company," Tom explained with a chuckle. Minutes later, the two boys were sound asleep. For a while, all was silent. Then the apartment's telephone rang, shattering the stillness. Tom struggled out of the depths of sleep, got up, and groped his way over to the wall phone. "Tom Swift Jr. speaking." A familiar voice asked, "Did it come?" "Oh, hi, Dad!" Tom replied, yawning. "Yes, Exman arrived in fine shape. We've put him to bed. Tell you all about it tomorrow morning." "Okay, Tom." As Tom hung up, Bud roused and switched on a lamp. He had awakened in time to catch only part of Tom's words. "Your father?" he inquired. Tom nodded sleepily and was about to go back to bed. But Bud, still fascinated by the space visitor, decided to have a peek at Exman. He got up and opened the door to the laboratory. A yell from him brought Tom rushing to his side. "Hey! It's gone!" The spot by the night light where they had left Exman was now deserted! Tom found a wall switch and pressed it. As light from the overhead fluorescent tubes flooded the room, the boys gave laughing cries of relief. Ole Think Box had merely moved himself to another corner of the room! "Guess he didn't like that little chum we left on for him," Bud said with a chuckle. "Let's leave him where he is," Tom agreed. The two boys went back to the adjoining apartment and were soon asleep again. Several hours later they were rudely awakened by a loud crash of glass and a heavy thud. "Something's happening to Exman!" Tom cried. With Bud at his heels, the young inventor dashed into the laboratory. CHAPTER XII EXMAN TAKES ORDERS A strange sight greeted Tom's and Bud's eyes. In the first rays of sunlight, the space robot was moving back and forth about the laboratory in wild zigzag darts and lunges. As he rolled toward a bench or other object, the brain energy seemed to send out invisible waves that knocked things over! Already the floor was strewn with toppled lab stools, books, and broken test tubes. The heavy thud had apparently been caused by a falling file cabinet. "Stop him!" Bud yelped. Exman was heading straight for a plate-glass window! Reaching from floor to ceiling, the glass formed one entire wall of the laboratory. "Oh, no!" Tom tensed, realizing that it was hopeless to try to stop Exman in time. But an instant later, the rolling robot stopped of its own accord, as if registering the fact that its energy waves were now striking a fragile surface. The thick pane of glass vibrated in its frame.