“Diamorphine hydrochloride,” I murmured mechanically.

“This method of taking the drug is very common on the other side. Another proof, if we wanted one, that the man came from Canada or the States.”

“What first attracted your attention to that summerhouse?” I asked curiously.

“My friend the inspector took it for granted that anyone using that path did so as a shortcut to the house, but as soon as I saw the summerhouse, I realized that the same path would be taken by anyone using the summerhouse as a rendezvous. Now it seems fairly certain that the stranger came neither to the front nor to the back door. Then did someone from the house go out and meet him? If so, what could be a more convenient place than that little summerhouse? I searched it with the hope that I might find some clue inside. I found two, the scrap of cambric and the quill.”

“And the scrap of cambric?” I asked curiously. “What about that?”