They had moved Mr. Copperdock’s body until his back was visible. There, just below the left shoulder-blade, was an almost circular patch, covered with a curious white powdery incrustation. In the centre of this patch was an angry looking purple spot.

The doctor bent over this and uttered an exclamation of amazement. Opening the case which he had laid down by his side he took from it a pair of forceps, and applied them to the spot on Mr. Copperdock’s back. From this he withdrew something, which he carried over to the light, and beckoned to Whyland to inspect.