The Sergeant remained silent, thinking his own thoughts, till we entered the plantation of firs which led to the quicksand. There he roused himself, like a man whose mind was made up, and spoke to me again.

"Mr. Betteredge," he said, "as you have honoured me by taking an oar in my boat, and as you may, I think, be of some assistance to me before the evening is out, I see no use in our mystifying one another any longer, and I propose to set you an example of plain speaking on my side. You are determined to give me no information to the prejudice of Rosanna Spearman, because she has been a good girl to YOU, and because you pity her heartily. Those humane considerations do you a world of credit, but they happen in this instance to be humane considerations clean thrown away. Rosanna Spearman is not in the slightest danger of getting into trouble - no, not if I fix her with being concerned in the disappearance of the Diamond, on evidence which is as plain as the nose on your face!"

"Do you mean that my lady won't prosecute?" I asked.

"I mean that your lady CAN'T prosecute," said the Sergeant. "Rosanna Spearman is simply an instrument in the hands of another person, and Rosanna Spearman will be held harmless for that other person's sake."

He spoke like a man in earnest - there was no denying that. Still, I felt something stirring uneasily against him in my mind. "Can't you give that other person a name?" I said.

"Can't you, Mr. Betteredge?"

"No."

Sergeant Cuff stood stock still, and surveyed me with a look of melancholy interest.

"It's always a pleasure to me to be tender towards human infirmity," he said. "I feel particularly tender at the present moment, Mr. Betteredge, towards you. And you, with the same excellent motive, feel particularly tender towards Rosanna Spearman, don't you? Do you happen to know whether she has had a new outfit of linen lately?"

What he meant by slipping in this extraordinary question unawares, I was at a total loss to imagine. Seeing no possible injury to Rosanna if I owned the truth, I answered that the girl had come to us rather sparely provided with linen, and that my lady, in recompense for her good conduct (I laid a stress on her good conduct), had given her a new outfit not a fortnight since.

"This is a miserable world," says the Sergeant. "Human life, Mr. Betteredge, is a sort of target - misfortune is always firing at it, and always hitting the mark. But for that outfit, we should have discovered a new nightgown or petticoat among Rosanna's things, and have nailed her in that way. You're not at a loss to follow me, are you? You have examined the servants yourself, and you know what discoveries two of them made outside Rosanna's door. Surely you know what the girl was about yesterday, after she was taken ill? You can't guess? Oh dear me, it's as plain as that strip of light there, at the end of the trees. At eleven, on Thursday morning, Superintendent Seegrave (who is a mass of human infirmity) points out to all the women servants the smear on the door. Rosanna has her own reasons for suspecting her own things; she takes the first opportunity of getting to her room, finds the paint-stain on her night-gown, or petticoat, or what not, shams ill and slips away to the town, gets the materials for making a new petticoat or nightgown, makes it alone in her room on the Thursday night lights a fire (not to destroy it; two of her fellow-servants are prying outside her door, and she knows better than to make a smell of burning, and to have a lot of tinder to get rid of) - lights a fire, I say, to dry and iron the substitute dress after wringing it out, keeps the stained dress hidden (probably ON her), and is at this moment occupied in making away with it, in some convenient place, on that lonely bit of beach ahead of us. I have traced her this evening to your fishing village, and to one particular cottage, which we may possibly have to visit, before we go back. She stopped in the cottage for some time, and she came out with (as I believe) something hidden under her cloak. A cloak (on a woman's back) is an emblem of charity - it covers a multitude of sins. I saw her set off northwards along the coast, after leaving the cottage. Is your sea-shore here considered a fine specimen of marine landscape, Mr. Betteredge?"

I answered, "Yes," as shortly as might be.

"Tastes differ," says Sergeant Cuff. "Looking at it from my point of view, I never saw a marine landscape that I admired less. If you happen to be following another person along your sea-coast, and if that person happens to look round, there isn't a scrap of cover to hide you anywhere. I had to choose between taking Rosanna in custody on suspicion, or leaving her, for the time being, with her little game in her own hands. For reasons which I won't trouble you with, I decided on making any sacrifice rather than give the alarm as soon as to-night to a certain person who shall be nameless between us. I came back to the house to ask you to take me to the north end of the beach by another way. Sand - in respect of its printing off people's footsteps - is one of the best detective officers I know. If we don't meet with Rosanna Spearman by coming round on her in this way, the sand may tell us what she has been at, if the light only lasts long enough. Here IS the sand. If you will excuse my suggesting it - suppose you hold your tongue, and let me go first?"

If there is such a thing known at the doctor's shop as a DETECTIVE-FEVER, that disease had now got fast hold of your humble servant. Sergeant Cuff went on between the hillocks of sand, down to the beach. I followed him (with my heart in my mouth); and waited at a little distance for what was to happen next.

As it turned out, I found myself standing nearly in the same place where Rosanna Spearman and I had been talking together when Mr. Franklin suddenly appeared before us, on arriving at our house from London. While my eyes were watching the Sergeant, my mind wandered away in spite of me to what had passed, on that former occasion, between Rosanna and me. I declare I almost felt the poor thing slip her hand again into mine, and give it a little grateful squeeze to thank me for speaking kindly to her. I declare I almost heard her voice telling me again that the Shivering Sand seemed to draw her to it against her own will, whenever she went out - almost saw her face brighten again, as it brightened when she first set eyes upon Mr. Franklin coming briskly out on us from among the hillocks. My spirits fell lower and lower as I thought of these things - and the view of the lonesome little bay, when I looked about to rouse myself, only served to make me feel more uneasy still.