"How _terribly_ interesting, Dr. Lane! I'm afraid you didn't film a very amusing stereop, though. A film without a plot or a hero--" Gary glared at her irately. "Uninteresting, eh?" he growled. "A plotless story? Very well--see for yourself! Here!" And he tossed on the desk before his _confrères_ a set of prints. Bryant, Anjers and the girl moved forward to look at them. Gary and Flick glanced at one another, wondering if their associates would read into the pictures that which they had seen and, seeing, scarcely dared believe. For a long moment there was silence. Then the small visiting scientist raised his head. He said, "This is a very interesting series of exposures, my young friend. But what a shame your camera moved!" Gary laughed triumphantly. "That's just it, Doctor! The camera did not move an inch! The 'motion' in that comet is the very thing I've been talking about!" He bent over the pictures, jabbing an excited finger at a faint white speck in the upper corner. "Here is the story caught by Muldoon's camera. When this first picture was taken, the comet was far out in extra-galactic space. It had not yet hurled itself into the galaxy of which our solar system is a part. Its position on the two subsequent photographs enable us to determine, accurately and perfectly, the comet's spatial trajectory. "But look at the _fourth_ photograph! What do you see there?" Dr. Bryant said bewilderedly, "Why, that's odd! The comet seems to have departed from its original trajectory; it is bent at almost a 45° angle from its former line of flight. That must be where the camera moved." "I tell you again," swore Gary, "that camera did not move! The action you see depicted on those prints is but one of two things: either the motion of the comet, itself, or--" He breathed deeply, then plunged--"or the effect worked upon the comet's light-rays by its presence in our galaxy!" * * * * * Dr. Anjers glanced at him with swift concern. "What is that? Our galaxy! I am afraid you have been overworking, my young friend--" "Just a moment, Doctor! I have further proof." The younger man's hands dug into his portfolio. "Dr. Bryant, let me ask you a question. If you were asked to declare the most baffling of all astronomical puzzles, what would you select?" "Why--why, I suppose the 'red shift', Gary." "Exactly! From the early Nineteenth Century to this day, one riddle which has amazed and confounded scientists is the apparent movement of our universe. According to all evidence, our universe is composed of a multitude of galaxies--each of which is running away from all others at unbelievable speed. "This we know because of the 'red shift'--which one might call the 'Doppler effect' applied to light, rather than to sound. When one star, comet or galaxy approaches another, pressing its light waves upon its neighbor, the cosmic body's light waves are shortened. They shift toward the violet side of the spectrum.