Penny was disheartened at the information. With the museum attendant out of the city, she could not hope to be of assistance to Amy Coulter. The situation looked very dark for the young sculptress unless other clues regarding the identity of the art thief were discovered soon.

“I wonder if this man Hoges really did go away on a vacation?” Penny mused. “He certainly vanished at the psychological moment!”

Giving no hint of what was in her mind, she politely thanked the guard for the information and returned home. After leaving her packages she called upon Susan to relate the adventures of the day.

“I think you were wise to tell Amy to hide,” Susan approved. “We know her story is true, but it doesn’t sound that way.”

Penny was not certain that her father would take a similar viewpoint. She intended to tell him about Amy that evening and ask his advice regarding the situation, but directly after dinner Mr. Nichols isolated himself in his study, devoting himself to a new case upon which he was working.

In the morning at breakfast Penny did manage to bring up the subject, but Mr. Nichols listened inattentively as he sipped his coffee.

“I don’t believe you heard a word I said,” Penny complained finally.

“What was that? Oh, yes, I did. You were saying something about Amy Coulter.”

“Never mind,” Penny sighed. “I can tell your mind is a million miles away tracking down a wicked criminal.”

“I hope the villain hasn’t gone that far,” Mr. Nichols chuckled. “Oh, by the way, you might tell Mrs. Gallup I’ll not be home for dinner.”

Penny regarded her father severely.

“Dad, have you forgotten what day this is.”

“Tuesday the twentieth.”

“This is the night of Mrs. Archibald Dillon’s big reception.”

The detective looked disconcerted. “I forgot all about it,” he admitted. “How I hate those affairs unless I’m there on a salary watching for gem thieves! Mrs. Dillon is the worst social climber in Belton City.”

“Just the same we accepted this invitation and we’ll have to go,” Penny said sternly.

“I can’t make it. I have important work to do.”

“But Dad ”

“You go alone, Penny, and do the honors for the family. Tell Mrs. Dillon that I came down with croup most unexpectedly. Tell her anything you like, only count me out.”

“She’ll never forgive you if you don’t go. Can’t you possibly make it?”

Mr. Nichols frowned in annoyance. “I suppose I might be able to drop around late in the evening. Possibly in time to take you home.”

“That would be better than not attending at all.”

“All right, we’ll leave it that way then. I’ll meet you about eleven o’clock tonight at Mrs. Dillon’s.”

The detective hastily kissed his daughter goodbye and hurried away to the office.

Penny did not look forward to the coming party. While Mrs. Dillon’s receptions were always elaborate, usually they were boring. Susan had not been invited and she doubted that many young people would attend.

Penny sighed as she reflected that she might have spent a pleasant evening with a book. But she brightened a trifle as it occurred to her that the party would give her an opportunity to wear her new blue evening gown and silver slippers.

Eight o’clock found her en route to the Dillon residence in a taxi. The car swung into a curving drive and halted in front of an imposing, white colonial house. A liveried servant opened the automobile door for her and Penny joined several other guests who were entering the marble hallway.

“Miss Penelope Nichols,” announced a servant.

It was all very formal and made Penny feel slightly ill at ease. She paused dutifully to greet her hostess.

Mrs. Archibald Dillon, a plump woman, well past middle age, was gowned in an elegant beaded dress, low-cut and far too conspicuous for the occasion. She had acquired wealth through marriage, but while she was active in many clubs and various types of charity work, she had never been able to achieve her social ambitions.

“My dear, didn’t your father come with you?” she inquired, giving Penny’s hand a slight pressure.

“No, Mrs. Dillon, he was detained at the office on an important case. However, he will surely drop in before the evening is over.”

Penny selected a chair in a quiet corner of the reception room and surveyed the throng. She saw few persons she actually knew although many she recognized from having seen their photographs in the newspapers. A long line of chairs along the north wall was completely unoccupied. Apparently, Mrs. Dillon had expected far more guests than had arrived.

A listless orchestra played for dancing, but only a few couples were moving about the floor. There were no young people present. The only interesting feature of the party was the expensive costumes of the guests. Many of the women wore elaborate evening gowns of velvet and bright silk, adorning themselves with glittering diamonds, which however, could not compete with a string of matched pearls proudly displayed by the hostess.

“This party resembles a style show,” Penny thought. “As far as I’m concerned it’s going to be a big flop.”

Mrs. Dillon presently left her post near the door and circulated among her guests, trying to create a false air of conviviality. Noticing that Penny sat alone, she came over to her.

“My dear, aren’t you dancing? I shall find a nice partner for you.”

Before Penny could protest, the woman hurried away, returning almost immediately accompanied by a man in evening dress. Penny was dismayed to recognize Hanley Cron. Upon seeing her, he paused, and a look of keen displeasure crossed his face.

Unaware that she was creating an awkward situation, Mrs. Dillon gushingly introduced the two. Hanley Cron bowed coldly.

“We’ve met before,” Penny said.

“Oh! Then you’re old friends.”

Penny politely refrained from comment, but Hanley Cron said coldly, in a tone which made his meaning very clear:

“Hardly that.”

“Acquaintances I should have said,” Mrs. Dillon murmured in embarrassment.

“You will pardon me I hope,” Hanley Cron observed aloofly. Turning his back upon Penny he walked away.

“Oh, my dear, I’m terribly sorry,” Mrs. Dillon fluttered. “I’ll find you another partner.”

“Please don’t,” Penny pleaded. “I really have no wish to dance at all.”

“Of course, if that’s the way you feel ”

“It is, Mrs. Dillon. I really am enjoying myself just watching the others.”

Penny’s statement was not quite true, for she had derived no pleasure from the party, and the rebuff she had received was quite enough to make her wish that she had remained at home. However, the reply served to satisfy the woman and she mercifully moved on to talk with another guest.

“Hanley Cron is the most ill-mannered man I ever met,” Penny thought indignantly. “I wish Dad would come, then I could go home.”

Her eyes smoldered wrathfully as she watched the art critic talking with a group of people near the refreshment table. She knew it was silly to allow herself to become annoyed because of his insulting manner, yet it was quite impossible to dismiss the man from her mind.

Not wishing to even see him again that evening, she arose and explored the veranda. It was crowded so she came indoors again and wandered through the rooms adjoining the reception hall. The library was entirely deserted.

Penny peered with interest at the books which lined the wall cases. Most of them did not appear to have ever been used. Selecting one at random she curled herself comfortably in an upholstered chair, sitting with her back to the door.

“I’ll just stay in here for an hour or so and read,” she decided. “No one will miss me.”

The book was interesting and when Penny glanced at the little clock on the table she was surprised to see that it was nearly eleven o’clock.

“Dad should be coming along soon,” she told herself. “He’ll be wondering what became of me.”

Reluctantly she closed the book. Before she could leave her chair to put it away she heard voices just outside the library door.

Mrs. Dillon and a feminine guest entered the room. They were talking in low tones.

“I haven’t told a soul except you,” Mrs. Dillon declared. “Before I show you my treasure, you must promise never to reveal my secret. I shouldn’t care to be arrested.”

“Of course I promise,” the other agreed.

Neither of the women was aware of Penny’s presence in the library for she was concealed behind the high back of the chair. The girl hesitated to reveal herself, for already she had heard enough to cause Mrs. Dillon embarrassment. She decided to remain where she was and keep quiet.

Mrs. Dillon carefully closed the library door and to Penny’s amazement, locked it.

“I don’t want to risk having anyone come in,” she explained to her companion. “As it is, my husband is quite provoked at me for making the purchase. It was such a wonderful bargain I couldn’t resist. But he is afraid someone will learn of it.”

“You did take a chance in buying it,” the other woman remarked.

“Oh, the trouble will soon blow over and if I should be caught I can always plead innocence. The dealer assured me I could sell it at any time for twice what I paid.”

The floor creaked beneath Mrs. Dillon’s weight as she crossed the room. The woman halted in front of a large picture which hung over the mantel. By this time Penny was overcome with curiosity. Risking detection, she peeped out from behind her chair.

Mrs. Dillon reached up and jerked a long silken rope which was suspended from the picture. Immediately it swung aside, revealing a hidden opening in the wall.

Mrs. Dillon drew back a blue velvet curtain and waited expectantly for her friend’s praise. Exposed to view was a small oil painting.

Penny recognized it as the stolen Rembrandt.