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 bedroom. 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.