Penny shook her head. "I'm not so sure of that, Sue. It looks to me as if these numbers have been changed. Wait a minute!" She darted into the house, returning with her father's magnifying glass. Using it to study the figures upon the wheel, the girls could plainly see that the numbers had been altered. "To think I'd buy a stolen wheel!" Susan exclaimed indignantly. "I'm going right back and tell that dealer a thing or two!" "You can't very well do that. We would be in no position to prove anything." "I suppose you're right," Susan admitted. "I'd like to see the establishment where you bought the tire," Penny said after a moment's pause. "Could you point it out to me?" "Yes, I'll take you there now if you like." Penny rolled the lawn mower into the garage and climbed into the coupé beside her chum. "How do you like your car by this time?" she inquired as they drove toward South Lake Street. "Not so well. It starts hard and has a funny sound in the engine. In a few days I mean to take it back to the Brunner garage for a complete overhaul." South Lake Street was located in the poorer section of Belton City. The neighborhood was noted for its second-hand stores and it was said that sooner or later stolen merchandise found its way into the crowded little shops which lined the narrow thoroughfare. Often wares were piled upon the sidewalks to attract an unwary buyer. Stoves, cheap tables, and all manner of hardware rubbed elbows with clever brass jugs, imported vases and Oriental rugs. Presently, Susan halted her car in front of a tire shop which was located at the outskirts of "second hand" row. "This is the place," she announced. The owner of the shop, a short, squat little man with beady black eyes, stood at the window. He eyed the girls sharply. "Shall we go in?" Susan asked. "Let's, but we mustn't act as if we suspect anything." Assuming a casual attitude, they sauntered into the shop. The dealer recognized Susan instantly. On her first visit he had been a trifle too cordial, but now he regarded her shrewdly. "Something?" he inquired. "My friend wishes to buy a new wheel," Susan informed. "She'd like to see one like I bought yesterday." Again the dealer cast a sharp glance at Penny. "Haven't I seen you in here before?" he asked. Penny shook her head. "No, this is the first time I ever came into your store." "I've seen you somewhere," the man muttered. "Now, I know! You're Christopher Nichols' daughter!" He pronounced the name of the detective with a slight sneer. "Yes, I am," Penny acknowledged reluctantly. "But I'm sure I've never seen you before." "That's quite likely." "Then how did you know me?" "That's my business," the dealer retorted shortly. "I am sorry, but I can't do business with you. Good day." Penny stood her ground. "Haven't you any tires for sale?" "Not for you, I haven't. You're a snooper just like your father! Get out of here!"