She slowly mounted the stairs and disappeared into her own room. CHAPTER VIII A Revealing Clue For the next few days Penny saw very little of her father. He left the house early in the morning and often did not return at night until after she had retired. Meals became something of an ordeal, for either Mr. Nichols buried himself in a newspaper or allowed the conversation to lapse. "You're as talkative as the sphinx!" Penny accused. "Is the case going badly?" "Not to my knowledge." "Is it going well then?" "Not especially." "Have you found any clue as to the whereabouts of Rap Molberg?" "Not yet." "You're impossible!" Penny cried furiously. "It's no use trying to learn a thing from you unless you're in exactly the right mood!" In desperation she sought solace in the companionship of her chum, Susan. They attended a great many moving picture shows and developed an enviable tan by swimming outdoors and playing tennis for hours at a time. Although Penny was permitted complete freedom, Mr. Nichols had warned her to use caution whenever she left the house at night. On more than one occasion in going downtown or to the home of a friend, she half suspected that she was being followed. She refrained from mentioning her fear to Mr. Nichols lest he curtail her freedom. But she became more alert and watchful. One afternoon while Penny was mowing the yard, Susan drove up in her coupé. It was the first time she had used it since the unfortunate night of the theft. She hailed Penny joyously. "The old bus is traveling again! It has a new generator and a fine new wheel!" Penny inspected the new purchases. "See anything wrong with the wheel?" Susan demanded. "Not a thing. Why?" "I bought it for about half the regular price. I was a little afraid I might have been gipped." Penny examined the spare wheel more critically. "It looks exactly like the one Dad bought me some time ago for nine ninety-eight. In fact, I'd think it was the same tire--the one that was stolen from me--if I didn't know better." "I only paid four dollars," Susan informed proudly. "Wasn't it a bargain?" "It looks like it. Where did you buy the tire?" "Oh, at a little place on South Lake Street. I don't remember the name." "South Lake isn't such a good location," Penny said thoughtfully, "I've heard Father say that a great many disreputable firms operate there. I know once he traced stolen furniture to a dealer on that street." "I hope I didn't buy a stolen wheel," Susan declared. "Was that what you had in mind, Penny?" "I thought of it right off. But I haven't any reason for saying it. For all I know, your tire may be a legitimate bargain." "I wish there was some way of finding out for certain," Susan said anxiously. "Let's look for the serial number. The wheel should have one." Penny moved closer to inspect the new purchase. "The number is here all right," she acknowledged. "Then the tire wasn't stolen," Susan said in relief.