It was at that stage of his reverie that a sudden byplay of movement captured his attention. In an instant he had cupped his cigarette into his palm, stepped into a dark patch of shadow. A figure had glided from the passageway that led to the sleeping quarters, was now peering uncertainly into the observation deck. It was David Wilmot, one of the six passengers aboard the _Libra_. Wilmot's thin face was pinched with nervousness; he coughed, a thin little hacking sound in the muted quiet, then put the back of his hand to his mouth. Dan stood motionless, his dark uniform blending perfectly with the drapes that concealed him. As he waited, watching, the door at the far end of the deck opened, a short, plump man in night-robe entered. Wilmot sprang forward eagerly. His whisper carried to Dan's keen ears. "Have you got them, Doctor?" "Quiet, you fool!" Dr. Bonetti's forehead creased angrily; his eyeglasses reflected a subdued light owlishly. He fumbled in his pocket, passed something white to the other man. "Here! But not a word, about this, mind you!" "I know. I know." Wilmot seized the papers avidly, turned and fled down the corridor whence he had emerged. The doctor stared after him for a moment, shook his head regretfully, then disappeared. The door closed behind him softly. "_That's why, too, we must keep our eyes open--._" The skipper's words echoed in Dan Mallory's memory as he stepped from his hiding place, brow furrowed. What the devil was going on here? Could Bonetti have been the bearer of the secret plans; could Wilmot have been the spy? Had he just witnessed the sell-out of a traitor? But before he could get his jumbled thoughts into order, a voice addressed him from behind, gravely, quietly. "Rather confusing, eh, Lieutenant?" Dan whirled to look into the face of Garland Smith, another of the _Libra's_ passengers. He said, half pettishly, "You, Captain? What are _you_ doing up at this time of night?" * * * * * The one-time officer of the SSP, now on the retired list, shot a swift glance at the glittering panorama visible through the quartzite plates. "Night, Lieutenant? Night and day are nothing but quirks of speech out here, sleep a matter of habit. When you have lifted gravs as many years as _I_ have--" He sighed. "I was restless. And perhaps it is just as well. I witnessed the same thing you did. And strange things are going on aboard the _Libra_." Mallory said cautiously, "Perhaps you're too apprehensive, Captain. Just because two passengers are sleepless like yourself, meet in the observation chamber--"