Mr. Franklin was as close at hand as could be - waiting for his first chance of being introduced to the great Cuff. In half a minute he was in the room, and was giving his evidence as follows:

"That door, Sergeant," he said, "has been painted by Miss Verinder, under my inspection, with my help, and in a vehicle of my own composition. The vehicle dries whatever colours may be used with it, in twelve hours."

"Do you remember when the smeared bit was done, sir?" asked the Sergeant.

"Perfectly," answered Mr. Franklin. "That was the last morsel of the door to be finished. We wanted to get it done, on Wednesday last - and I myself completed it by three in the afternoon, or soon after."

"To-day is Friday," said Sergeant Cuff, addressing himself to Superintendent Seegrave. "Let us reckon back, sir. At three on the Wednesday afternoon, that bit of the painting was completed. The vehicle dried it in twelve hours - that is to say, dried it by three o'clock on Thursday morning. At eleven on Thursday morning you held your inquiry here. Take three from eleven, and eight remains. That paint had been EIGHT HOURS DRY, Mr. Superintendent, when you supposed that the women-servants' petticoats smeared it."

First knock-down blow for Mr. Seegrave! If he had not suspected poor Penelope, I should have pitied him.

Having settled the question of the paint, Sergeant Cuff, from that moment, gave his brother-officer up as a bad job - and addressed himself to Mr. Franklin, as the more promising assistant of the two.

"It's quite on the cards, sir," he said, "that you have put the clue into our hands."

As the words passed his lips, the bedroom door opened, and Miss Rachel came out among us suddenly.

She addressed herself to the Sergeant, without appearing to notice (or to heed) that he was a perfect stranger to her.

"Did you say," she asked, pointing to Mr. Franklin, "that HE had put the clue into your hands?"

("This is Miss Verinder," I whispered, behind the Sergeant.)

"That gentleman, miss," says the Sergeant - with his steely-grey eyes carefully studying my young lady's face - "has possibly put the clue into our hands."

She turned for one moment, and tried to look at Mr. Franklin. I say, tried, for she suddenly looked away again before their eyes met. There seemed to be some strange disturbance in her mind. She coloured up, and then she turned pale again. With the paleness, there came a new look into her face - a look which it startled me to see.

"Having answered your question, miss," says the Sergeant, "I beg leave to make an inquiry in my turn. There is a smear on the painting of your door, here. Do you happen to know when it was done? or who did it?"

Instead of making any reply, Miss Rachel went on with her questions, as if he had not spoken, or as if she had not heard him.

"Are you another police-officer?" she asked.

"I am Sergeant Cuff, miss, of the Detective Police."

"Do you think a young lady's advice worth having?"

"I shall be glad to hear it, miss."

"Do your duty by yourself - and don't allow Mr Franklin Blake to help you!"

She said those words so spitefully, so savagely, with such an extraordinary outbreak of ill-will towards Mr. Franklin, in her voice and in her look, that - though I had known her from a baby, though I loved and honoured her next to my lady herself - I was ashamed of Miss Rachel for the first time in my life.

Sergeant Cuff's immovable eyes never stirred from off her face. "Thank you, miss," he said. "Do you happen to know anything about the smear? Might you have done it by accident yourself?"

"I know nothing about the smear."

With that answer, she turned away, and shut herself up again in her bed-room. This time, I heard her - as Penelope had heard her before - burst out crying as soon as she was alone again.

I couldn't bring myself to look at the Sergeant - I looked at Mr. Franklin, who stood nearest to me. He seemed to be even more sorely distressed at what had passed than I was.

"I told you I was uneasy about her," he said. "And now you see why."

"Miss Verinder appears to be a little out of temper about the loss of her Diamond," remarked the Sergeant. "It's a valuable jewel. Natural enough! natural enough!"

Here was the excuse that I had made for her (when she forgot herself before Superintendent Seegrave, on the previous day) being made for her over again, by a man who couldn't have had MY interest in making it - for he was a perfect stranger! A kind of cold shudder ran through me, which I couldn't account for at the time. I know, now, that I must have got my first suspicion, at that moment, of a new light (and horrid light) having suddenly fallen on the case, in the mind of Sergeant Cuff - purely and entirely in consequence of what he had seen in Miss Rachel, and heard from Miss Rachel, at that first interview between them.

"A young lady's tongue is a privileged member, sir," says the Sergeant to Mr. Franklin. "Let us forget what has passed, and go straight on with this business. Thanks to you, we know when the paint was dry. The next thing to discover is when the paint was last seen without that smear. YOU have got a head on your shoulders - and you understand what I mean."

Mr. Franklin composed himself, and came back with an effort from Miss Rachel to the matter in hand.

"I think I do understand," he said. "The more we narrow the question of time, the more we also narrow the field of inquiry."

"That's it, sir," said the Sergeant. "Did you notice your work here, on the Wednesday afternoon, after you had done it?"

Mr. Franklin shook his head, and answered, "I can't say I did."

"Did you?" inquired Sergeant Cuff, turning to me.

"I can't say I did either, sir."

"Who was the last person in the room, the last thing on Wednesday night?"

"Miss Rachel, I suppose, sir."