He was aloft alone now, courting death--instant, invisible death. He wouldn't descend until that carnival of murder was at an end. But it was not at an end. Another crash, far up Pennsylvania Avenue, showed an attempt upon the Capitol. Again--again, and a smoking hell wreathed the noble buildings so that it was no longer possible to see them. A lull, and then a crash nearer the city's heart. Crash! Crash! Invisible though the enemy was, it was easy to trace the movements of this particular plane by the successive areas of destruction that it left behind it. It was coming back over Pennsylvania Avenue, dropping its bombs at intervals. It was methodically wiping out an entire section of Washington. Dick drove his plane toward it. There was one chance in a thousand that, if he could accurately gauge the progress of his invisible antagonist, he could crash him and go down with him to death. If he could get close enough to feel his prop-wash! A wild chance, but Dick's mind was keyed up to desperation. He shot like an arrow toward the scene, with a view to intercepting the murderer. Then of a sudden he became aware of a curious phenomenon. A black beam was shooting across the sky. A black searchlight! It came from the flat top of a large hotel that had somehow escaped the universal destruction, and, with its gaunt skeleton of structural steel showing in squares, towered out of the ruin all about it like an island. * * * * * It was from here that the black beam started. It spread fanwise across the sky. But it was not merely blackness. It was utter and impenetrable darkness, cleaving the sky like a knife. Where it passed, the rays of the moon were extinguished as fire is extinguished by water. A beam of absolute blackness, that pierced the air like a widening cone, and made the night seem, by contrast, of dazzling brightness along either dark border. High into the air that dark beam shot, moving to and fro in the sky. Dick, darting toward the spot where he hoped to find his invisible enemy, found himself caught in it. In utter, inextinguishable darkness! Like a trapped bird he fluttered, hurling himself this way and that till suddenly he found himself blinking in the dazzling light of the moon again, and the black beam was overhead. Crash! Another widening sphere of ruin as the invisible marauder dropped a bomb. Dick cursed bitterly. Trapped in that black beam, he had lost his direction. The invisible plane had shot past the point where he had hoped to intercept it. He flung his soaring lever, and hung suspended in the air. An easy mark for the enemy, if he chose to take the opportunity. No matter. Death was all that Dick craved. He had seen half his flight wiped out, and a hundred thousand human beings hurled to destruction. He wanted to die.