To their relief, he smiled when he saw them.
"Come in," he invited.
Frank and Joe entered the study.
"Did you catch any auto thieves?" asked their father.
The boys were astonished.
"How did you know we were after auto thieves, Dad?" asked Frank.
"It doesn't take a great deal of perception to find that out," their father answered. "All these mysterious doings can have only one reason."
"Well, we didn't catch any," Joe admitted.
"I didn't think so. They've been busy to-night."
"Again!"