All at once Steve felt the flooring drop from beneath his feet; and, without making a sound, the lad plunged over into the darkness. A loud splash followed, then all was still. CHAPTER XXI THE SEARCH FOR THE MISSING BOY Bob Jarvis waited a long time at the chutes for his companion, but Steve did not return. This did not cause Bob any particular worry, as Steve no doubt had been called to some other part of the mine. So Bob deciding to wait no longer, strolled away. At the close of the day's work, however, when Steve was not at the mouth of the shaft waiting for him, Bob began to wonder. He waited about the shaft for half an hour, then went on to his boarding place. Steve had not returned. "Where's Rush?" demanded the boarding boss, knowing Steve's habit of punctuality. "That is what's bothering me. I haven't seen him." It was the business of the boarding boss to look quickly into any absences and report them to the superintendent or the mine captain. He got busy at once. Calling up the time-keeper's office, he inquired if Steve Rush had checked in. The information came back a moment later that Steve had not come up from the mine yet; or, if he had, he had failed to report himself. "Then something has happened to him," was Jarvis' emphatic conclusion. "He left word for me to meet him at seventeen, but when I got there he had gone. I haven't seen him since." The boarding boss agreed so strongly that he telephoned to the superintendent. The latter had not yet arrived home from his office, so the mine captain was communicated with. But Bob Jarvis already was out of the house, headed for the shaft at top speed. "Has Steve Rush come up yet?" he demanded of the cage-tender. "Haven't seen him." Bob hesitated. He realized the futility of wandering about the mine not knowing in what part of it he should look for the missing Steve. He then hurried to the time-keeper's office, learning that nothing had been seen of the missing boy. Bob did not know which way to turn. But by the time he had reached the shaft again Superintendent Penton was there, together with the mine captain, preparing to go below. The cage had just come up and the men were stepping aboard when a boy from the boarding house where the Iron Boys lived came running up out of breath. "Wait!" cried Bob. "Here comes a boy from our hashery. Maybe Steve has gone home." "What is it, boy?" called the superintendent. "Boss wanted me to tell you that the telephone man who lives with us says Mr. Rush got a telephone message from you to meet him at the lower level this afternoon. He says Rush didn't come back." "I didn't send for him to meet me anywhere," answered the superintendent. "We'll go to the lower level. Shoot us down as fast as is safe," he added, addressing the cage-tender. The bottom of the car seemed to be dropping from beneath their feet, so rapid was their descent. Bob, holding to the support rod above their heads, was thinking fast and hard.