Tuppence watched him drive off in the car with a faint misgiving. Tommy was very sure-she herself was not so sure. There were one or two things she did not quite understand.

She was still standing by the window, watching the road, when she saw a man leave the shelter of a gateway opposite, cross the road and ring the bell.

In a flash Tuppence was out of the room and down the stairs. Gladys Hill the parlormaid, was emerging from the back part of the house, but Tuppence motioned her back authoritatively. Then she went to the front door and opened it.

A lanky young man with ill-fitting clothes, and eager dark eyes was standing on the step.

He hesitated a moment, and then said.

"Is Miss Kingston Bruce in?"

"Will you come inside?" said Tuppence.

She stood aside to let him enter, closing the door.

"Mr. Rennie, I think?" she said sweetly.

He shot a quick glance at her.

"Er-yes."

"Will you come in here, please?"

She opened the study door. The room was empty, and Tuppence entered it after him, closing the door behind her. He turned on her with a frown.

"I want to see Miss Kingston Bruce."

"I am not quite sure that you can," said Tuppence composedly.

"Look here, who the devil are you?" said Mr. Rennie rudely.

"International Detective Agency," said Tuppence succinctly-and noticed Mr. Rennie's uncontrollable start.

"Please sit down, Mr. Rennie," she went on. "To begin with, we know all about Miss Kingston Bruce's visit to you this morning."

It was a bold guess, but it succeeded. Perceiving his consternation, Tuppence went on quickly.

"The recovery of the pearl is the great thing, Mr. Rennie. No one in this house is anxious for-publicity. Can't we come to some arrangement?"

The young man looked at her keenly.

"I wonder how much you know," he said thoughtfully. "Let me think for a moment."

He buried his head in his hands-then asked a most unexpected question.

"I say, is it really true that young St. Vincent is engaged to be married?"

"Quite true," said Tuppence. "I know the girl."

Mr. Rennie suddenly became confidential.

"It's been hell," he confided. "They've been asking him here morning, noon and night-chucking Beatrice at his head. All because he'll come into a title some day. If I had my way-"

"Don't let's talk politics," said Tuppence hastily. "Do you mind telling me, Mr. Rennie, why you think Miss Kingston Bruce took the pearl?"

"I-I don't."

"You do," said Tuppence calmly. "You wait to see the detective, as you think, drive off and the coast clear, and then you come and ask for her. It's obvious. If you'd taken the pearl yourself, you wouldn't be half so upset."

"Her manner was so odd," said the young man. "She came this morning and told me about the robbery, explaining that she was on her way to a firm of private detectives. She seemed anxious to say something, and yet not able to get it out."

"Well," said Tuppence. "All I want is the pearl. You'd better go and talk to her."

But at that moment Colonel Kingston Bruce opened the door.

"Lunch is ready, Miss Robinson. You will lunch with us, I hope. The-"

Then he stopped and glared at the guest.

"Clearly," said Mr. Rennie, "you don't want to ask me to lunch. All right, I'll go."

"Come back later," whispered Tuppence, as he passed her.

Tuppence followed Colonel Kingston Bruce, still growling into his moustache about the pestilential impudence of some people, into a massive dining-room where the family was already assembled. Only one person present was unknown to Tuppence.

"This, Lady Laura, is Miss Robinson who is kindly assisting us."

Lady Laura bent her head, and then proceeded to stare at Tuppence through her pince nez. She was a tall thin woman, with a sad smile, a gentle voice, and very hard shrewd eyes. Tuppence returned her stare, and Lady Laura's eyes dropped.

After lunch Lady Laura entered into conversation with an air of gentle curiosity. How was the inquiry proceeding? Tuppence laid suitable stress on the suspicion attaching to the parlormaid, but her mind was not really on Lady Laura. Lady Laura might conceal teaspoons and other articles in her clothing, but Tuppence felt fairly sure that she had not taken the pink pearl.

Presently Tuppence proceeded with her search of the house. Time was going on. There was no sign of Tommy and, what mattered far more to Tuppence, there was no sign of Mr. Rennie. Suddenly Tuppence came out of a bedroom and collided with Beatrice Kingston Bruce who was going down stairs. She was fully dressed for the street.

"I'm afraid," said Tuppence, "that you mustn't go out just now."

The other girl looked at her haughtily.

"Whether I go out or not is no business of yours," she said coldly.

"It is my business whether I communicate with the police or not, though," said Tuppence.

In a minute the girl had turned ashy pale.

"You mustn't-you mustn't-I won't go out-but don't do that." She clung to Tuppence beseechingly.

"My dear Miss Kingston Bruce," said Tuppence smiling.

"The case has been perfectly clear to me from the start-I-"

But she was interrupted. In the stress of her encounter with the girl, Tuppence had not heard the front door bell. Now, to her astonishment, Tommy came bounding up the stairs, and in the hall below she caught sight of a big burly man in the act of removing a bowler hat.

"Detective Inspector Marriot of Scotland Yard," he said with a grin.

With a cry, Beatrice Kingston Bruce tore herself from Tuppence's grasp and dashed down the stairs, just as the front door was opened once more to admit Mr. Rennie.

"Now you have torn it," said Tuppence bitterly.

"Eh?" said Tommy, hurrying into Lady Laura's room. He passed on into the bathroom, and picked up a large cake of soap which he brought out in his hands. The Inspector was just mounting the stairs.

"She went quite quietly," he announced. "She's an old hand, and knows when the game is up. What about the pearl?"

"I rather fancy," said Tommy, handing him the soap, "that you'll find it in here."

The Inspector's eyes lit up appreciatively.

"An old trick, and a good one. Cut a cake of soap in half, scoop out a place for the jewel, clap it together again, and smooth the join wed over with hot water. A very smart piece of work on your part, sir."

Tommy accepted the compliment gracefully. He and Tuppence descended the stairs. Colonel Kingston Bruce rushed at him and shook him warmly by the hand.

"My dear sir, I can't thank you enough. Lady Laura wants to thank you also-"

"I am glad we have given you satisfaction," said Tommy. "But I'm afraid I can't stop. I have a most urgent appointment. Member of the Cabinet."

He hurried out to the car and jumped in. Tuppence jumped in beside him.

"But Tommy," she cried. "Haven't they arrested Lady Laura, after all?"

"Oh!" said Tommy. "Didn't I tell you? They've not arrested Lady Laura. They've arrested Elise."

"You see," he went on, as Tuppence sat dumbfounded, "I've often tried to open a door with soap on my hands myself. It can't be done-your hands slip. So I wondered what Elise could have been doing with the soap to get her hands as soapy as all that. She caught up a towel, you remember, so there were no traces of soap on the handle afterwards. But it occurred to me that if you were a professional thief, it wouldn't be a bad plan to be maid to a lady suspected of kleptomania who stayed about a good deal in different houses. So I managed to get a photo of her as well as of the room, induced her to handle a glass slide and toddled off to dear old Scotland Yard. Lightning development of negative, successful identification of fingerprints-and photo. Elise was a long lost friend. Useful place, Scotland Yard."

"And to think," said Tuppence, finding her voice, "that those two young idiots were only suspecting each other in that weak way they do it in books. But why didn't you tell me what you were up to when you went off?"

"In the first place, I suspected that Elise was listening on the landing, and in the second place-"

"Yes?"

"My learned friend forgets," said Tommy. "Thorndyke never tells until the last moment. Besides, Tuppence, you and your pal Janet Smith put one over on me last time. This makes us an square."