“This is the limit,” he thought. “For all I know, there may be no regular lock at all. Instead, there may be a mechanism somewhere else, operating a series of bolts which can be shot into the door from all sides. I might have known that any safe Carter would have would not be as easy to crack as this one seemed to be. Curse him! I wish I had him here right now! I’d make him open this safe for me, or tear him to pieces with my bare hands!” Much must be allowed for exaggeration in the case of an angry man. If Nick Carter could have appeared at that moment, it is probable that the outcome would have been by no means the one Green Eye imagined. After storming up and down the room a few times, Gordon quieted down a little and returned to the safe. It had occurred to him that in the absence of anything like a knob or handle, there must be a secret spring or something of that sort, that was pressed in order to set the mechanism in motion, and open the inner door. If he could find that, all would be well. It seemed like a hopeless task, but Green Eye was master of himself again, and prepared to exercise the greatest care and perseverance. First, he returned Nick’s tools to the little black bag, and restored it to the drawer, after which he carefully removed all traces of his work, except those which permanently disfigured the outer door, and told of the violation of its lock. Even these he cleverly hid by means of a sort of wax, which he found in Nick’s laboratory, and which he coated over with ink after the holes had been plugged. He did not expect to use the tools again, if he could help it, and he wished to clear the telltale litter away before doing anything else, so that if he were interrupted, in spite of his injunctions, he could open the door without too great delay. Another trip to the detective’s desk brought to light a powerful magnifying glass. Armed with this, the rascal returned to the safe and began a systematic inspection of its surfaces, inward and outward, so far as he could gain access to them. He was looking for some place where the enamel had been worn off by the frequent pressure by fingers, or where finger marks had been left in such a way as to indicate repeated pressures. He began just beyond the edge of the narrow door, and worked his way completely around it, but without success. “I didn’t think I’d find it there,” he told himself, “but I had to make sure first.” He then extended his area of search, taking in the jambs of the outer door, and so working his way out to the exterior of the safe. He did not waste time over the inside of the outer door, for his common sense told him that there could be no connection between that and the rest of the safe, except through the hinges, which were not likely to conceal any hidden wiring or mechanical connection.