"Well, at least we've discovered what it was we ran through at the moment we hit the beach," I offered. "All we need to do is find a way through it, and go on with our maneuver." Ziegler shook his head. "No, sir, I don't see it like that. We can see through this stuff, or seem to, but we can't see back the way we came, astern of the landing craft." "Right, corporal; what do you think it is, then?" "I'm no scientist, sir. I'd say it is a net of some kind, in which we have been caught, landing craft and all, like so many fish. But by whom? By what? For what reason? It has me stopped." "I wonder--" began Preble, then stopped, staring at the place where he and Ziegler had come to a dead stop. Preble stepped back. In his arms he cradled one of the latest automatic weapons. Preble stepped back, lifted the muzzle of the weapon, held down the trigger for a few squirts. The weapon acted naturally enough. There was no question that the bullets left the muzzle of the fast-firer. But we didn't hear them hit the invisible screen; nor, looking beyond it, did we see where the bullets kicked up sand. The bullets simply plunked into nothingness as bullets of an obsolete day vanished into soap or sand during firing tests. A few seconds passed. Then there were soft sounds in the sand at the very spot where the two marines had hit the wall. All three of us looked down. The flattened, steel-jacketed bullets lay in a small group in the sand, within a couple of inches of the invisible wall--on our side of it. "Caught the bullets, like a baseball catcher!" said Preble, his voice high-pitched with threatened hysteria. "Then just dropped 'em! Took them in, killed their speed, then slowly discarded them! And I saw the wall do it!" Ziegler and I had not seen this phenomenon, but we were not directly behind the weapon, as Preble was. I lifted my binoculars for the first time and looked around at the other patrols, all of which I could see easily. All except those which followed a southerly direction had come to the wall and were just as puzzled by it as we. None of us had anything to offer; we were even afraid to think lest we question our own sanity. We held our ground until all patrols had come up against the invisible wall. Then we had some idea of the extent of our prison. That brooding mountain to the south, it appeared, was forbidden to us. How high did the wall reach? Was it domed? "Preble, fire as nearly straight up as you can," I told the private. "Then we'll duck away fifty or sixty yards, just in case, and listen." Ziegler and I stepped well back. Preble took careful aim. He squirted a few score slugs, then ran to join us. We were so silent we could not even hear each other's breathing. Shortly we heard the bullets drop into the sand, and stepped forward.