"You mean they mingle with underworld characters and try to gain their confidence?"
"Yes, that's the usual plan. When I locate Rap Molberg I'll have him constantly shadowed."
"I've never seen many of your assistants around the office," Penny remarked.
"Naturally not," Mr. Nichols smiled. "If they came here to report, every crook in Belton City would be aware of it within an hour."
"Then how do you keep in touch with your men?" Penny asked curiously.
"There are a few secrets which I must keep to myself. Aren't you taking a rather sudden interest in my work, Penny?"
"Perhaps I am. Since my car wheels were stolen I feel personally concerned in the case. I wish I could do something to help."
Mr. Nichols became grave. "There is nothing you can do, Penny. The last thing in the world that I could wish would be to have you involved in the case. In fact I've been worried for fear——"
"For fear of what?" Penny demanded as her father checked himself.
"I've been afraid that the Molberg gang might attempt to strike at me through you. Until this case is finished you must be very careful."