"All hands below!" came the order. Immediately the deck guns were made fast and the crew scrambled down through the hatches. In a few minutes, driving ahead at full speed, the _Dewey_ was submerged until only her periscopes showed. All at once the crew heard a shout from the conning tower. "There she is!" yelled Lieutenant McClure, as he stood with his eyes glued to the periscope glass. "U-boat driving straight ahead at the smoke curtain. Port the helm!" he commanded. The _Dewey_ came around sharp and, in response to the guidance of her commander, began to ascend. Having executed a flank movement, the _Dewey_ now was endeavoring to engineer a surprise attack on the German submarine from the rear. To all intents, the German commander had not yet noted the approaching American submersible. He was going after the transports full tilt, hoping to bore through the destroyers' smoke curtain and torpedo one of the Yankee fleet. Quickly the _Dewey_ dived up out of the water, the hatches were thrown open and the gun crews swarmed on deck, carrying shells for their guns. Jack and Ted followed Mike Mowrey on deck and dropped into position behind "Roosey." Gazing ahead they could make out the German periscope and its foamy trail. "Fire on that periscope," ordered Lieutenant McClure. The U-boat was not more than nine hundred yards away, according to the _Dewey's_ range-finder, and apparently yet unconscious of the proximity of the American submarine. In a moment the gun was loaded and ready for firing. "Bang!" she spoke, and then every eye followed the shot. Commander McClure had jumped up on the conning tower and was hugging the periscope pole. There was a moment's silence before he spoke. "A little short, boys," he called. "Elevate just a little more---you've nearly got the range." Again the gun crew leaped into action. "Hurry, boys! he sees us now and is beginning to submerge!" yelled the young lieutenant as he followed the U-boat through his glasses. Again "Roosey" spoke, and this time with an emphatic "crack" that boded ill for any luckless human who might get within the line of its screaming shell fire. "O-o-o-oh, great!" cried Lieutenant McClure an instant later as he peered more intently through his glasses. Of a sudden the periscope disappeared from the crest of the sea as though wiped out completely by the explosion of the _Dewey's_ shell. "No doubt of it, boys; you ripped off that periscope," announced McClure, with an air of finality. At their commander's words the gun crew burst into cheers. The submersible's wireless was singing out a message of good cheer to the American fleet. It was only too evident that the enemy U-boat had been crippled and put completely to rout by the daring maneuvers and deadly gunfire of the _Dewey_. "Who said the Yanks couldn't stop their pesky undersea wasps?" chattered Bill Witt joyously. "If they just let us loose long enough we'll show 'em how to kill poison with poison."