"I've had enough punishment! That makes the third straight set you've won."
"It's getting almost too dark to see the ball," Penny said generously. "Shall we call it an evening and finish off with something to eat?"
They crossed over to Eby's Café, a favorite haunt of Belton City's younger set. The booths were quite deserted.
"Everyone seems to have gone away for the summer," Susan mourned as she pondered over the menu. "I suppose you'll be leaving soon too, Penny."
"No chance of it, I'm afraid. Dad has become involved in a new case which may keep us in town indefinitely."
"I wish my father were a detective," Susan commented a trifle enviously. "It's too bad about the vacation of course, but your life is exciting at least."
It seemed to her that Penny always led an unhampered, adventurous existence. At any rate, the girl was well acquainted with interesting happenings at the Belton City police court and had more than a nodding acquaintance with fascinating personages of the city.
"I've never had any real adventures," Penny declared gloomily. "Unfortunately, Dad is a little secretive about his sleuthing activities. I'd give anything to know about this latest case----"
Her voice trailed off for the two girls had heard a shrill warning whistle which they instantly recognized as the fire siren. Although they had not even begun their suppers they rushed to the plateglass window to watch the red engine clatter by.
"Why, it's turning down our street!" Susan exclaimed. "Oh, I hope our house isn't afire!"
"Let's jump in my car and follow," Penny proposed.
They hurriedly left the café. Penny had parked her roadster just out of sight around the corner. But as they viewed the car, they both stopped short in amazement.
"The rear wheel is gone!" Susan gasped. "Surely that can't be your roadster, Penny!"
It had grown quite dark outside and for an instant both girls believed they had made a mistake in identifying the car. Yet one glance at the license number assured them that they had made no error. A daring thief had jacked up the rear axle, stealing an almost new wheel which Penny's father had purchased for her only the previous week. An inspection disclosed that the spare wheel also had been taken.