"I wish you could see the picture," she ended. "I'm almost certain it's a fake. If I can smuggle you into the library, will you look at it?"

"No, Penny, I will not. You seem to forget that we're guests of Mrs.

Dillon."

"Yes, but if she has the stolen Rembrandt in her possession, isn't it our duty to notify the police?"

"Do you know that she has the stolen painting?"

"No, in fact I rather suspect she's been cheated by a dishonest dealer."

"In that event, you'd only stir up a hornet's nest without doing a particle of good. In fact, exposing Mrs. Dillon might give the real thief a warning to lie low."

"How do you mean, Dad?"

"Why, the moment Mrs. Dillon is arrested, the dealer from whom she purchased the picture will disappear. Then there will be no way to trace the real thief."

"You're a.s.suming that the dealer and the thief worked together even though the painting which Mrs. Dillon bought may have been a fake."

"It's quite possible, Penny. Some day when the time is more opportune, I'll explain to you how picture thieves work their racket. For the moment I wish you'd accept my opinion that this case is packed with dynamite. My advice to you is to be very sure of what you're doing before you start any action."

"I guess you're right," Penny agreed. "I'll not do anything rash."

"The case may shake down in a few days," Mr. Nichols went on. "In the meantime, Mrs. Dillon isn't going to dispose of her picture. She'll not find it as easy to sell as she antic.i.p.ates."

The detective arose from the bench after glancing at his watch.

"We'll have to go inside now," he said, "or the party will be over."

They entered the house and after wandering about for a few minutes encountered Mrs. Dillon. She greeted the detective cordially and the smile she bestowed upon Penny disclosed that she had not even noticed the girl's long absence from the ballroom.

"How do you like her?" Penny whispered to her father as they sought the refreshment table.

The detective shrugged. "She serves very good punch."

Mr. Nichols knew nearly all of the guests, either personally or by reputation. Penny noticed that as he appeared to talk casually with one person after another, actually he was surveying the throng somewhat critically.

"You were right about the jewelry," he said in an undertone to his daughter. "That necklace Mrs. Dillon is wearing must be worth at least a cool ten thousand dollars."

"I should think she'd be afraid of losing it," Penny commented.

"Oh, it's probably insured for all it's worth," Mr. Nichols returned casually.

The orchestra had struck up again and as other couples went out on the floor, Penny tugged at her father's sleeve.

"Come on, Dad. Let's dance."

"You know I hate it, Penny."

"Just one," she pleaded. "I've had no fun at all this evening."

"Oh, all right," he gave in. "But remember, one dance is the limit."

"That depends upon how many times you step on my feet," Penny laughed.

Actually, Christopher Nichols was a far better dancer than he imagined himself to be. His steps were introduced in a mechanical routine which sometimes annoyed Penny, but otherwise he made an excellent partner, gliding smoothly over the floor with the ease and grace of a young man.

"How am I doing?" he mumbled in his daughter's ear as he whirled her deftly about to avoid striking another couple.

"Not bad at all," Penny responded, smiling. "Consider yourself engaged for the next dance."

"Only one I said. I don't want to be laid up with rheumatism tomorrow."

"Rheumatism!" Penny scoffed.

She had spoken the word in an ordinary tone but it sounded as if she had shouted it for the music ended unexpectedly in the middle of a strain, trailing off into discordant tones. The amazed dancers halted, looking toward the orchestra to see what was wrong.

Penny felt the arm which her father held about her waist stiffen. A scream of terror rippled over the room.

Two men with white handkerchiefs pulled over their faces, had entered the ballroom through the double French doors opening into the garden.

They trained their revolvers upon the dancers.

"This is a stick-up!" one announced grimly. "Put up your hands and stand against the north wall!"

CHAPTER VII

An Invitation to Lunch

Penny and her father were forced to line up with the other guests.

They stood against the north wall, their hands held above their head.

Members of the orchestra and servants were compelled to obey the order.

While one of the holdup men covered the crowd with his revolver, the other moved swiftly from person to person collecting jewelry, watches and money.

Penny saw Mrs. Dillon, pale and frightened, trying to drop her pearl necklace into a flower pot, but she was not quick enough. The holdup man jerked the string from her hand.

"Oh, no you don't, lady," he snarled. He admired the pearls an instant before dropping them into a small cloth bag which he carried.

Penny stood next in line. She wore no jewelry save an inexpensive brooch which had belonged to her mother. Tears came into her eyes as the thief jerked it from her dress.

"Oh, please don't take that--" she began.

"Make no resistance," Mr. Nichols ordered curtly.

Penny relapsed into silence. She was a trifle puzzled at her father's att.i.tude for she had always imagined that in such a situation he would be the first to fly into action.

The holdup man paused in front of the detective.