CHAPTER VIII.

  EXPLOSIVES FOR THE GATUN DAM.

  Ned and Jimmie listened for some moments to the steady click-click ofmetal which came, or appeared to come, from the ground directly underneaththeir feet, and then Ned arose and crept forward.

  "Where you goin'?" whispered Jimmie.

  "Down there."

  Ned pointed to the dark corner.

  "You'd better come away," warned the boy.

  "We are here to investigate," Ned replied, almost impatiently.

  "Then investigate with a bomb, or with a cannon," advised Jimmie.

  "No time for that," came the reply. "The conditions which exist now maynot exist in an hour's time. It is now or never."

  Moving forward, Ned saw a faint finger of light cutting the shadows in thecorner Jimmie had pointed out. Jimmie saw it at the same instant.

  "I'll bet they've got a blacksmith shop down there," he said.

  There was no opening in the great stone slabs of the floor through which aman might make his way--only the crevice through which the ray of lightcame. Ned turned his attention to the wall to the south.

  Behind a luxuriant growth of vines he saw another glimmer of light, and ina moment stood looking down a narrow stairway, at the distant end of whichwere numerous lines of red flame. Jimmie, looking over Ned's shoulder,uttered a muffled exclamation.

  "Looks like a door made out of red-hot bars," he said.

  "It is a board door," Ned whispered back, "with wide cracks between theplanks. There is an intense red fire in the room beyond."

  Ned placed a foot on the top step of the stairway and slowly andcautiously rested the weight of his body upon it, to make certain that notrap for the protection of the place had been set there. The stone stepwas solid and bore his weight firmly.

  At the bottom of the stairway the boys stopped and looked about. Straightahead was the cracked door, to the south was a solid wall, to the north,under the stone pavement they had crossed to gain the corner, was a darkroom, the door to which stood open. The room was close and hot.

  "How are your matches, Jimmie?" whispered Ned.

  "Got a pocketful," was the reply. "Want a light?"

  "Not yet. We would better feel our way into the room. Keep close to me andkeep your gun handy."

  The room was small, something like a vestibule to a larger one which ranalong parallel with the one from which the light came. It was very darkthere, and more than once the boys stumbled over obstructions on thefloor, which seemed to be of brick or stone. Once Ned heard Jimmielaughing softly as he rolled on the floor.

  "I'm thinkin' what the movin' picture men are missin'," the boy said, ashe moved forward on his hands and knees.

  "This would look rather amusing--on a white canvas on the Bowery," Nedsaid.

  After reaching a wall, the stones of which felt damp and oozy to thetouch, Ned ventured to light a match. The underground room was long andnarrow, with rock walls in which there was no opening except the one byway of which the boys had entered.

  Ned, by the flaring light of the match, brushed away the mould whichflourished in that unwholesome place and seated himself on the stonefloor, his back against the wall. Jimmie, seeking physical companionship,nestled close to him.

  "Gee," the little fellow remarked, with a snicker, "you thinkin' of takin'up a homestead here?"

  "I'm going to remain in this room until the workers in the other chambergo away," was the reply. "I've taken a notion to look into thatapartment."

  "And if they don't go away?"

  "I'll wait until they do. It is probable that they do all their work atnight."

  "Then you won't have to wait long," the boy replied. "It was growing lightin the east when we came down here."

  Jimmie dropped off into a restless sleep after a time, and Ned sat therewaiting and listening, just as Frank, a short time later, waited andlistened on the porch of the cottage in the jungle. When the boy awoke itwas with a start of anxiety.

  "The boys will think we're dead," he exclaimed.

  "I hope they won't try to follow us," Ned whispered.

  "If they do," the other said, "they'll find signs in twigs and stones allthe way along. The stone heaps point the way to this place, and give thewarning at the place where the stairs begin."

  Reference was here made to Boy Scout methods used in the forest. Forinstance, a stone with a smaller one on top says:

  "This is the trail."

  Place a stone to the right of this and the meaning is:

  "Turn to the right."

  One to the left means:

  "Turn to the left."

  A smaller stone on top of the other two, with none at the side, means: "Becareful."

  "I hope they will keep away," Ned went on. "It is a miracle, almost, thatwe got in here without being discovered."

  "What you think you'll find in there?" asked Jimmie.

  "Something concerning the plot," was the reply.

  It seemed a long time before the work in the chamber ceased, and Ned hadplenty of time in which to review the strange case he was interested in.The transition from gay New York to that weird apartment seemed almostlike a whiff of fancy. Then he recalled the painstaking surveillance ofthe fellow called "His Nobbs" on the way down, and smiled at the thoughtthat the plans he had made at first sight of the spy had worked outremarkably well.

  He had submitted gracefully to the surveillance, knowing that in time theman who was following him would track him to his camp on the Isthmus. Thatwas the very point. He would not know where to look for the plotters, butthey would know where to look for him. He depended on them to send a manto work him mischief, and reckoned on being able to follow that man backto his principals.

  This they had done. The men who had employed the spy on the ship had actedquickly and had sent a bomb-thrower. Ned shuddered as he thought of therisk he had taken that night in going to bed without leaving a guard. Hehad overlooked a point in the game there, for he had not apprehended suchprompt action on the part of the men he had pitted himself against.

  However, the plan had miscarried because of his waking at the criticalmoment, and here he was, at the door of the men who had sent the man abouttheir murderous work. But were these the principals? When he thought ofthe two who had hastened off toward Gatun in a motor car he did notbelieve that they were.

  "I shall have to look in other places besides subterranean chambers forthe men in charge," he thought. "These fellows are merely tools."

  Presently the sharp click-click of metal came no more through the heavyair of the room, and Ned, awaking Jimmie, who had fallen asleep again,moved into the small room from which the doorway gave a view of thestairs. He could see from this room that the sun was shining brightlyoutside.

  Ned had scarcely stationed himself in the heavy shadows back of thedoorway when four men came down the passage and passed him. He had nodoubt that they were the workmen going out for the day. Such work as theydid must needs be done in the night.

  Two of the men were tall and slim, with Spanish-looking faces, and twowere short and stout, with a heavy droop to their shoulders and broadfaces almost entirely covered with whiskers.

  "The original anarchists," whispered Jimmie, as the two short men passed.

  After the disappearance of the workmen all was still in the undergroundrooms. The door to the work-chamber had been left open, and Ned knew thatone of two things was the solution to this.

  Either there were other men in the room, or there were watchers on theoutside. He ventured out in the passage at the foot of the stairs andlooked up. A roughly-dressed man stood half in view, his back to thewatcher. When Ned turned back he saw Jimmie disappearing into thework-room. He called softly to him, but the boy passed on through thedoorway and was lost to sight.

  Annoyed at the unnecessary risk taken by the boy, Ned stepped back intothe room he had just left and waited half expecting to hear a call forassistance. He knew that he could be of more assistance there than in theopen doorway to the
room which the boy had entered. There he would atleast have the first shot if Jimmie was pursued and made for the stairs.

  While he waited almost holding his breath, he grasped the bomb he hadbrought with him from the cottage. If Jimmie should be killed in there,the bomb should avenge his death. The ruins of the temple and thework-shop of the plotters should all ascend heavenward in one grandexplosion. After a time, however, his fears were set at rest by theappearance of the boy, who came up to the doorway with a grin on hisface.

  "Nothin' stirrin' in there now," he said. "Come on."

  It seemed plain now that those interested in the work which was going onunderground were depending on outside watchers to protect them. The firein a rude forge which stood at the distant end of the chamber was dyingout when the boys reached it, and the place was only dimly lighted.

  On one side of the room was a pile of gas-pipe, cut in six-inch lengths.In a corner, far away from the fire, and half buried in the earth--a greatpaving stone having been removed to make way for the excavation--were tinvessels tightly covered. After his experiences of the night, Ned did nothave to inspect the contents of these tins. He knew very well that theycontained high explosives.

  "There's stuff enough here to blow up the continent of South America,"Jimmie said, pointing at the gas-pipe lengths and the tin vessels.

  "And they are getting the material in shape to do the work," Ned added.

  "Yep," Jimmie answered. "We've caught 'em with their workin' clothes on.We've got to the bottom of the plot."

  "You go too fast, son," Ned replied. "We haven't got a single clue to themen higher up. It is probable that we have discovered the plant of the menwho are planning to destroy Uncle Sam's big job, but the work we haveundertaken has only begun."

  "Why, catch these men," said Jimmie, "an' you've got 'em."

  "Got these men, yes, but the chances are that even they do not know themen who are at the head of the conspiracy."

  "Some one is puttin' money into it, anyway," the boy suggested.

  "Yes, and we don't even know the interests which are doing it," said Ned.

  Ned now busied himself about the chamber, having closed the door so thatthe light of his matches would not show. There was, of course, danger thatthe watcher might descend the stairs and discover the closed door, butthere was also the chance that he might attribute the changed situation toaccident.

  Presently Ned came upon a battered old writing desk standing on the headof a large barrel. The slanting top was locked down, but the boy soon hadit open. Its contents consisted of two rolls of drawing paper.

  Ned took them out, stirred the fire to a sudden glow, and bent over thefigures and lines on the sheets. His face grew thoughtful as he looked.

  "What is it?" Jimmie asked.

  Ned held out the rolls.

  "This one," he said, "is a drawing of the Gatun dam, and this other is acrude sketch of the basement of the _Daily Planet_ building in New York."

  "Gee!" cried the boy. "Are they goin' to blow that up, too?"

  "They appear to be thinking of it," was the reply. "And there on themargin of the sheets, of each of the sheets, is a date line--Saturday,April 15th. This is the 13th."

  "Is that the date set for the explosion?" asked the boy, with wide-openeyes.

  "I don't know," was the reply, "but it seems to me that we ought to getout of here and communicate with Lieutenant Gordon, and also with Mr.Shaw, in New York. The date marked here may be the one set for action."

  They started at once for the door, Ned taking the sheets with him andhoping to pass the guard without being seen. As they moved forward,however, they heard voices, and then a square of light told them that thedoor which they had left closed had been opened, and that three men wereentering.

  "If they turn on the light now," Jimmie whispered in Ned's ear, "there'llbe somethin' doin' here."

  The newcomers did not light the flaring torches with which the room wasusually illuminated, but, closing the door, sat down near the forge.

  "I think," Ned whispered, drawing Jimmie toward the door, "that the fateof the Gatun dam and the _Daily Planet_ building depends on our gettingout of here. Move carefully."