The result was truly astonishing. The weak, chubby, girlish face had been changed by these few touches into the strong, coarse face of a middle-aged woman.

“It really is amazing!” I exclaimed. “It is a perfectly different face. I wouldn’t have believed that such a thing was possible.”

“It is a most striking and interesting demonstration,” said Thorndyke. “But yet I don’t know that we need be so surprised. If we consider that of all the millions of persons in this island alone each one has a face which is different from any other, and yet that all those faces are made up of the same anatomical parts, we realize that the differences which distinguish one face from another must be excessively subtle and minute.”

“We do,” agreed Marion, “especially when we are modelling a portrait bust and the likeness won’t come although every part appears to be correct and all the measurements seem to agree. A true likeness is an extraordinarily subtle and exact piece of work.”

“So I have always thought,” said Thorndyke. “But I mustn’t delay you any longer. May I have my precious parcel?”

Marion handed him the not very presentable bundle with a smile and a bow. He then took his leave of her and I escorted him to the door, where he paused for a moment as we shook hands.

“You are bearing my advice in mind, I hope, Gray,” he said.

“As to keeping clear of unfrequented places? Yes, I have been very careful in that respect, and I never go abroad without the pistol. It is in my hip-pocket now. But I have seen no sign of anything to justify so much caution. I doubt if our friend is even aware of my existence, and in any case, I don’t see that he has anything against me, excepting as Miss D’Arblay’s watch-dog.”

“Don’t be too sure, Gray,” he rejoined earnestly. “There may be certain little matters that you have overlooked. At any rate, don’t relax your caution. Give all unfrequented places a wide berth and keep a bright look-out.”

With this final warning, he turned away and strode off down the road while I re-entered the studio just in time to see Polton mix the first bowl of plaster, as Marion, having washed the clay from the transformed mask, dried it and rehung it on its peg.