A moment of strange whirling unreality. The control room seemed fading about me. The tube-lights dimmed. A green glow took their place--a lurid sheen in which the cubby and the tense faces of De Boer and Hans showed with ghastly pallor. Everything was unreal. The voices of De Boer and Hans sounded with a strange tonelessness. Stripped of the timber that made one differ from the other. Hollow ghosts of human voices. By the sound I could not tell which was De Boer and which was Hans. The corridor was dark; all the lights on the ship faded into this horrible dead green. The window beside me had a film on it. A dead, dark opening where moonlight had been. Then I realized that I was beginning to see through it once more. Starlight. Then the moonlight. We had soared almost level with the descending patrol-ship. We went past it, a quarter of a mile away. Went past, and it did not follow. It was still circling. * * * * * I knew then what had happened. And why this bandit ship had seemed of so strange an aspect. We were invisible! At four hundred yards, even in the moonlight, the patrol could not distinguish us. Only ten of these X-flyers were in existence: they were the closest secret of the U. S. Anti-War Department. No other government had them except in impractical imitations. I had never even seen one before. But this bandit ship was one. And I recalled that a year ago, a suppressed dispatch intimated that the Service had lost one--wrecked in the Lowlands and never found. So this was that lost invisible flyer? De Boer, using it for smuggling, with Perona and Spawn as partners. And now, De Boer making away in it with Spawn's treasure! The bandit's hollow, toneless, unreal chuckle sounded in the gruesome lurid green of the control room. "I think that surprised them!" The tiny silver shape of the baffled local patrol-ship faded behind us as we flew northward over heavy, fantastic crags; far above the tiny twinkling lights of the village of Nareda--out over the sullen dark surface of the Nares Sea. CHAPTER XIII _The Flight to the Bandit Stronghold_ During this flight of some six hours--north, and then, I think, northeast--to the remote Lowland fastness where De Boer's base was located, I had no opportunity to learn much of the operation of this invisible flyer. But it was the one which had been lost. Wrecked, no doubt, and the small crew aboard it all killed. The vessel, however, was not greatly damaged: the crew were killed doubtless by escaping poisonous gases when the flyer struck.