"Stay here and wait for any further message," he told himself. "Wonder if Drew and the rest will really come up to Iggy and his gang? If they do, man! oh, man!" He could just hear the guns popping. There was, however, no such luck, at least for the moment. As the happy, fighting four, Drew and his band, neared the garage at 1046 Blair Street, they saw a low, yellow sedan pop out of the garage door and go speeding north. "That's sure to be them. After them! Give her the gas!" the Captain shouted. Drew sent the Captain's powerful car speeding after. The yellow car shot straight north for a mile. Then it whirled round a corner on two wheels. When Drew and his band rounded that corner there was no car in sight--only a huge, lumbering moving-van two blocks to the east. "Street ends two blocks west," the Captain snapped. "Must have gone east. Drive slow and watch the north and south streets." This they did. They were still going slow as they passed the van. Spider, who had been sitting in the back seat with Tom Howe, was startled a moment later to find that Tom was no longer with him. He was not in the car. He was gone. * * * * * * * * In the meantime, Johnny Thompson was in the midst of a strange discovery. Ten minutes after the first message had been delivered, the bell began its jangle once more. "Hello!" Johnny exclaimed. "Big Ben again!" Springing to his feet, he began walking back and forth before the round reflector. As on the other occasion, the bell ceased jangling as he passed. A series of rapid experiments with a hat held in his hand showed him he could shut off the bell by holding the hat in certain positions. These positions, he found, must be higher and higher as he receded from the reflector toward the window. "One thing I know," he assured himself. "That sound is produced by some force outside my window. And the person who produces it must be very high up. "In fact--" He caught his breath as he looked out of the window and away to the east. "There is but one place it could come from. That is the top of the six hundred foot tower of the Sky Ride on those deserted Century of Progress grounds. The Whisperer--" He broke off short to listen with all his ears. The ringing of that bell ceased, the whispered message was beginning. * * * * * * * * What had happened to the slender young detective, Tom Howe? Something rather strange, I assure you. Having slipped from the slowly moving police car, he had mounted the running board of the vast lumbering van. From this point he slid to a position beside the driver. As he did this he prodded the driver in the ribs with an automatic and whispered, "You will drive as I say and where I say, or you are a dead man!" The driver never took his eye from the road. He drove straight on. * * * * * * * *