The girl looked at us from one to the other.  “You have seen her, then,” she said in a strange, muffled voice, and added:  “She isn’t dead, is she?  Not really dead?” The question was asked in a tone at once coaxing and despairing, such as a distracted mother might use over the corpse of her child.  It filled me with vague discomfort, and, unconsciously, I looked round towards Thorndyke.

To my surprise he had vanished.

Noiselessly backing towards the head of the stairs, where I could command a view of the hall, or passage, I looked down, and saw him in the act of reaching up to a shelf behind the street door.  He caught my eye, and beckoned, whereupon I crept away unnoticed by the party on the landing.  When I reached the hall, he was wrapping up three small objects, each in a separate cigarette-paper; and I noticed that he handled them with more than ordinary tenderness.

“We didn’t want to see that poor devil of a girl arrested,” said he, as he deposited the three little packets gingerly in his pocket-box.  “Let us be off.”  He opened the door noiselessly, and stood for a moment, turning the latch backwards and forwards, and closely examining its bolt.

I glanced up at the shelf behind the door.  On it were two flat china candlesticks, in one of which I had happened to notice, as we came in, a short end of candle lying in the tray, and I now looked to see if that was what Thorndyke had annexed; but it was still there.

I followed my colleague out into the street, and for some time we walked on without speaking.  “You guessed what the sergeant had in that paper, of course,” said Thorndyke at length.

“Yes.  It was the hair from the dead woman’s hand; and I thought that he had much better have left it there.”

“Undoubtedly.  But that is the way in which well-meaning policemen destroy valuable evidence.  Not that it matters much in this particular instance; but it might have been a fatal mistake.”

“Do you intend to take any active part in this case?” I asked.

“That depends on circumstances.  I have collected some evidence, but what it is worth I don’t yet know.  Neither do I know whether the police have observed the same set of facts; but I need not say that I shall do anything that seems necessary to assist the authorities.  That is a matter of common citizenship.”

The inroads made upon our time by the morning’s adventures made it necessary that we should go each about his respective business without delay; so, after a perfunctory lunch at a tea-shop, we separated, and I did not see my colleague again until the day’s work was finished, and I turned into our chambers just before dinner-time.

Here I found Thorndyke seated at the table, and evidently full of business.  A microscope stood close by, with a condenser throwing a spot of light on to a pinch of powder that had been sprinkled on to the slide; his collecting-box lay open before him, and he was engaged, rather mysteriously, in squeezing a thick white cement from a tube on to three little pieces of moulding-wax.