All Clo's efforts and schemings wasted! She had tricked, stolen, risked her life, in vain. The envelope was gone.

"You can't have looked everywhere," she insisted. "The thing must have got tucked out of sight—unless Miss Blackburne ... but no, she's as good as gold!"

"I'm sure you're right about her. She is good," said Beverley. "But ... she says nobody came into the room while she was there.... I asked her. Otherwise I might have thought that Rog——" The sentence broke. "I wanted to see you alone," Angel began again, "so I came back. You've been so wonderful to-day, you've made me depend upon you. If there were anything to do, you'd be the one to do it. But there's nothing ... is there? I can't see any light, can you?"

"Let me help you to look for the envelope," said Clo.

"Come, then," said the other, in a toneless voice, unlike her own. Together they went to Beverley's boudoir, where there was a little interlude of greetings between Clo and Miss Blackburne. Then, Clo was beginning her search for the lost envelope when Roger Sands slowly passed the half-open door. Beverley had left it ajar, not because she wished to call him (that desire had fled with the news about the pearls), but in order to see that he went out. She stood with her back to the door at the moment, but on the wall directly opposite hung a long mirror. Clo guessed, by the slight start Angel gave, that she must have caught sight of his reflection. He turned and came back.

"If he asks to see the pearls!" was the thought in Clo's head. Her eyes met Beverley's and read the same terror there.

Roger spoke to Miss Blackburne, pausing on the threshold.

"What do you think of the baubles?" he asked with elaborate carelessness. "Are they above the average?"

The two girls held their breath. Would the pearl-stringer give the situation away?

But Miss Blackburne, true to herself, was discretion incarnate.

"I've not seen enough of the pearls, yet, to form an opinion," she replied, "but my impression is that they must be altogether exceptional."

"I'm glad your impression is good," said Roger. He turned to his wife. "I may not be back till late. Don't sit up for me. Good-night."

Beverley followed him into the hall.

"Roger!" she pleaded. "You're doing me a most horrible injustice. I can't bear it!"

"What do you mean?" he asked.

"You can't help knowing," she said, "It's about Justin O'Reilly. You think I——"

"Have I accused you of anything?" he challenged, brows raised, eyes blank.

"No. But——"

"Your imagination seems to be even more lively than your conscience is sensitive, my dear girl. What have you done, that I should accuse you?"

"I've done nothing, Roger, that you——"

"All right, then. Why borrow trouble? I must hurry, or I'll miss my appointment. Good-night again. Sleep well!"

Roger left her without a backward glance. Beverley felt that she was caught in the folds of a vast net.

What was it Clo had said, that day? "There was once a mouse who gnawed a net——" Poor mouse, it had tried to-day to gnaw the net! It had gnawed one small hole, but even before the prisoner could struggle to get free, the hole had closed again. Still, the mouse was ready for another bout. It was a brave, bold mouse—a subtle mouse! For some strange reason her sole hope was in Clo.

During her absence the girl had searched the boudoir from end to end. Her sharp eyes had not missed a cranny big enough to hide a pin, to say nothing of a rope of pearls or a large envelope with five red seals. Both the pearls and the envelope must have been stolen. Were there two thieves, or only one?

With Roger's departure, and Beverley's return, the three women could talk with freedom, especially after Mrs. Sands' announcement to the butler that he would not be needed to serve dinner.

Miss Blackburne reiterated that she knew nothing of the envelope. She had had no thought for anything except the pearls. Their loss put her into an embarrassing position unless Mrs. Sands intended informing Mr. Sands and the police at once of what had happened.

"I saw by your face you didn't want me to speak when your husband came in," she said to Beverley, "so I hedged, and did the best I could without lying. I realized that you would want to be the one to break the news. But I suppose you have told him now? He'll send the police, or some private detective, won't he, to take evidence while I'm here?"

"I do want to get them back," Beverley answered. "But I haven't told my husband, and we can't have the police, or even a detective. That must seem not quite fair to you, Miss Blackburne. Whatever happens, you shan't suffer, I promise. I believe I know who has taken the pearls. If I'm right, it isn't exactly a theft. Perhaps if I go the right way about it, I can get them again. What's the good of worrying my husband, when in a day or two there may be nothing to worry about?"

"M-m-m," muttered Miss Blackburne, "I think you're wrong, Mrs. Sands. I have a feeling that Mr. Sands suspects."

"That the pearls are gone? How can he?" Beverley cried.

"I don't know, I only feel," the little woman repeated.

As the two had talked, Clo watched Miss Blackburne's face. It was with her as the pearl-stringer had said of herself: she "did not know—she could only feel" that the good little woman had something on her conscience, something that she was obliged to hide.

Clo had by this time succeeded in clearing her mind from cobwebs.

Suddenly a light shone like flame upon the mystery. "Peterson!" was the name that printed itself upon the girl's brain. "If he could have got into the flat, he could have stolen both the pearls and papers. Does Miss Blackburne know something, and if she does, why won't she tell?"

It occurred to Clo that, if she could have a few words with Miss Blackburne alone, perhaps the puzzle might be solved.

"Angel," she said, "if there's been a thief in this house, perhaps he's here still. With two manservants, you ought——"

Beverley waited for no more. Any straw was worth catching at. She couldn't wait to ring for Johnson. She rushed out of the boudoir, hoping to find the butler in the dining room. He was there. And while she explained that something had been stolen, that the flat must be searched, Clo got the chance she had wanted.

"Miss Blackburne, you're my friend!" she exclaimed. "This means life or death to me. I'm responsible for that envelope we've lost. Do, for the love of heaven, tell me what happened in this room while Mrs. Sands went out and left you here alone."

The pearl-stringer remained silent. She met Clo's great, imploring eyes without shrinking, but the girl saw that she breathed hard.

"If you don't want me to die, tell me!" Clo implored.

"My child, I would tell you, if I could," she stiffened herself. "But, you see," she finished, "there's nothing to tell. So, I can't."