He was sitting on a keg in an angle of the wall. He was leaning back against the boards behind him, a cob pipe between his teeth. His eyes, peering out of the jungle of beard that covered his face, were fixed speculatively on the three boys. Merry immediately stepped to the prospector's side. "Hello, Porter!" he yelled in his ear. The prospector probably grunted, although Frank could hear nothing. "I want to talk with you for a few minutes," Merry went on, in a manner calculated to disarm any suspicions Porter may have had. "Come up to the super's office, will you?" He stepped back. The prospector sat still on the keg for a moment, then slowly knocked the ashes from his pipe and stood up. Frank was congratulating himself that Porter was to make for Pardo's office without any further persuasion; but in this he was mistaken. Clancy stood on the prospector's right, Merry in front of him, and Ballard on the left--between the spot where, Porter was standing and the opening that led into the feed loft. The prospector slipped his pipe into his pocket, moving in a slow, sluggish way that suggested weariness. He was not weary, however. Suddenly, without warning of any sort, he put out one arm and threw Clancy sideways, so that he fell over a heap of crushed stone. Another moment and Porter had leaped for a flight of stairs and had vanished downward into the body of the mill. It was all so quickly done that Frank was taken by surprise. The thought flashed through his mind that Porter, unless he knew something about Professor Borrodaile and suspected why the boys were there, would not be showing his teeth in that fashion. An instant after the prospector had disappeared down the stairs, Frank jumped after him. Ballard followed close on Frank's heels; and Clancy, hastily picking himself up, stifled an exclamation of anger and rushed after Ballard. The stairs led down to the floor where the boxes were placed, and where the plates, whose silver recovered the gold from the ore, stretched the length of the mill. Amalgamators and batterymen were going and coming through all the pounding racket of this part of the establishment, but the prospector had somehow managed to lose himself. So suddenly and completely had Porter disappeared that it seemed little short of magical. Frank took three or four steps from the foot of the stairs, peering along the row of plates covered with dirty water from the battery boxes, and looking back into the shadowy recesses under the ore loft. He was asking himself if Porter would have had time to get away into the darkness back of the batteries, when a red-shirted amalgamator stepped to his side. "Lookin' fer Porter?" he yelled. Frank nodded. "He ducked out o' the door yonder," and the amalgamator, with a jerk of his thumb, indicated an opening that led out into the night. Ballard was nearest the door. He had heard the amalgamator, and whirled like lightning and dashed out of the mill and into the darkness.