“He must be mighty tired!” remarked Joe. “I wonder where on earth he came from?”

“Probably been up all night. When Dad gets hard at work on a case he forgets all about sleep. I’ll bet he found something.”

“Hope so. But I wish he’d wake up and tell us. I hate to go back to school without knowing.”

But Mr. Hardy had not awakened by the time the boys set out for school again, although they lingered until they were in danger of being late.

All afternoon they were tormented by curiosity. Where had their father been? What had he discovered? As soon as school was out they fled down the steps, broke away from a group of boys anxious to get up a baseball game, and shattered all records in their race for home.