d Susan had paid to the Hamilton building?

"I suppose I've been trailed everywhere to-night," she ventured
conversationally.

"You almost gave us the slip," one of the detectives told her with a
smile. "In fact, you did for awhile."

"When was that?"

"Right after you left the library."

"You turned off somewhere and we lost you for a time. Didn't locate
you again until you turned up at your own home."

Penny was relieved. The detectives could not possibly be aware of the
secret entrance into the Hamilton Plant. She would still be the first
to report the discovery to her father.

The detectives dropped Penny at her own home after explaining that it
might be necessary for her to appear in court later on to identify the
prisoner.

"I'll be very glad to do it," Penny promised.

As she ran up the front steps the door was flung open and Mrs. Gallup
rushed out to meet her. She flung her arms about the girl.

"Penny!" she cried tremulously. "How thankful I am that you are safe!
Your father came home fifteen minutes ago. Then we knew that the
telephone call was a fake."

"Where is Dad now?"

"He started for the police station."

"Then I guess he'll learn the truth in a few minutes if he's still
there."

"Tell me what happened, Penny."

In the midst of the tale, a car was heard on the driveway, and a minute
later Mr. Nichols entered the house. Although he was never inclined to
be demonstrative, the detective clasped his daughter in his arms and
Penny noticed that his hands trembled slightly.

"I've just heard the entire story at the police station," he told her.
"You gave me a terrific scare, Penny."

"I gave myself one, too. If it hadn't been for your men who shadowed
me, I'm afraid I'd never have returned to tell the tale."

"I doubt that the gangsters would have actually harmed you, but they
would have used you as a weapon to strike back at me. I am sorry about
having you trailed, Penny, but you understand my position. I was
afraid of this very thing."

"It's all right," Penny smiled. "Only your men aren't so clever at
keeping me in sight. I unintentionally gave them the slip earlier in
the evening."

Mrs. Gallup had gone to the kitchen to prepare sandwiches and an iced
drink. Taking advantage of her absence, Penny gave a detailed report
of her visit to the Hamilton Plant. At first her father listened
almost incredulously.

"It sounds fantastic, Penny. And yet, it's just the sort