Observing that an automobile stood by the fence, they both halted.

"Why, that is Walter Crocker's car!" Susan exclaimed in an undertone.

"He must have driven straight over here from Herman's place," Penny added. "Now what do you suppose he wants?"

The girls walked slowly on. As they drew near the automobile, Walter Crocker alighted and tipped his hat politely.

"How do you do, Miss Nichols," he said with a forced smile. "I'm not sure if you remember me or not."

"I remember you perfectly," replied Penny, hiding her uneasiness.

She was afraid that the man might have seen Susan and herself peeping through the window of the barn.

"I feel very grateful for the ride which you and your father gave me some nights ago," said Walter Crocker. "I must apologize for running off the way I did without thanking you. I was in such a hurry to reach my uncle's home."

Penny and Susan drew a breath of relief. They were glad that the man did not intend to question them concerning their latest actions.

"Oh, that was quite all right," Penny replied. "We a.s.sumed that you had gone on to Mr. Crocker's place."

The young man shifted his weight uneasily. "Oh, by the way," he said, "I don't suppose you found a package of letters in the rumble seat?"

"Letters?" repeated Penny.

"I thought perhaps they might have dropped from my pocket while I was riding with you."

"Were they valuable?" asked Penny very innocently.

"Only to me," answered Walter Crocker shortly. "But I must have them back. Do you mind if I look in the back end of your car?"

"You'd be welcome to search if it were here."

"Where is the car?" demanded the man, in his anxiety forgetting to be polite.

"I couldn't say right now, Mr. Crocker. My father has the automobile."

"When will he return?"

"Probably not before evening," Penny replied, thinking quickly. "You might drop back after supper. He should be here by then."

"Thank you," said Walter Crocker shortly.

He climbed into the car and drove away.

"That's a good one!" laughed Penny, highly amused. "He has lost the Crocker letters all right, and he thinks they may be in our car!"

"Don't you expect your father home before night?" asked Susan.

"Of course I don't know exactly when he'll come," chuckled Penny. "But I'd not be surprised to see him driving in any minute. I wanted to give myself plenty of time to examine the car before Mr. Crocker returns."

"What would you do if you found the letters, Penny?"

"I haven't thought that far," Penny admitted. "But the chance that they're in our car is a very slim one."

The girls stationed themselves on the front porch so that they would not miss Mr. Nichols when he drove in. Two hours later they glimpsed the car coming up k.n.o.b Hill.

Penny meant to tell her father everything that had happened during the day, but the detective seemed to have important matters on his mind.

When the girls ran down to the car to meet him, he responded absent-mindedly to their greetings and went on into the cottage.

"Penny!" exclaimed Susan. "There's another auto coming up the hill!"

"And it looks like Walter Crocker's car!" Penny cried in alarm.

"Quick! We've no time to lose!"

The girls darted to Mr. Nichols' automobile and lifted up the rumble seat. While Susan anxiously watched the road, Penny climbed up and peered into the bottom of the car.

"Susan, they're here!" she squealed in delight.

"And so is Walter Crocker," Susan muttered in an undertone. "He's looking right this way."

With her back turned to the approaching automobile, Penny deftly slipped the package of letters into the front of her dress. She pretended to keep on searching in the bottom of the car.

"Act as if everything is perfectly natural," she warned Susan in a whisper.

Mr. Crocker stopped his car with a jerk and sprang out. He glanced suspiciously at the girls as he came toward them.

"Oh, how do you do, Mr. Crocker," Penny said, climbing slowly down from the rumble. "Dad just drove in a minute ago. I was looking for your letters."

"Are they there?" the man asked sharply.

"Perhaps you ought to look," Penny replied, avoiding Susan's glance.

"I had just started to search when you drove up."

Walter Crocker climbed up on the step and made a careful examination of the interior of the automobile. Penny and Susan stood watching him with perfectly innocent faces. They knew that he would not find the letters.

The man did not like to give up.

"They may have been pushed up forward out of sight," he said. "Do you have a flashlight?"

"I'll get one from the garage," Penny offered.

She and Susan went into the building, lingering there while they enjoyed a good laugh at the expense of Walter Crocker.

They were just ready to return with the flashlight when Penny suddenly placed a restraining hand on Susan's arm.

"Wait!" she whispered.

Unaware that the girls were in the garage, Mrs. Masterbrook came hurrying from the cottage. She went directly toward Walter Crocker, her face convulsed with anger.

"Why did you come here?" she demanded. "You should have known better!"