To this course there could be no opposition. The plain-clothes man was called in and placed in charge of the corpse with strict instructions to let no one approach it unless he came with a written authority from Sir Frank or the Inspector. Then the three of us entered the doctor’s car and drove towards Cavendish Square.

On the way my chief said to me, “It is curious that I can’t call to mind ever having heard of a Dr. Weathered. He must have been a man of high standing in the profession, apparently; probably a consultant; and yet his name is quite strange to me. Do you happen to have heard it at any time?”

It was a difficult question for me. I dared not tell a lie which accident might expose at any moment; but still less dared I tell the whole truth.

“I have heard the name,” I replied, speaking as slowly as possible to give myself time to frame the least compromising answer. “Perhaps I ought to say that I heard it from one of his patients in the course of a confidential communication, so that I hardly know how far I am justified in making any use of what I heard.”

Tarleton promptly raised his hand.

“Not another word,” he enjoined to my intense relief. But my relief was qualified when he proceeded. “A confidence made to a medical man is as sacred in my view as a confession made to a priest. You will understand that, Captain Charles, I am sure. We must not ask Dr. Cassilis to tell us anything more.”

Captain Charles assented rather reluctantly I thought. His original disapproval of me seemed to revive at the same time. He stole furtive glances at me now and then, as though he were wondering whether it was prudent on his part to keep such doubtful company.

The gold repeater in Tarleton’s fingers kept time to his meditations till the car drew up in front of a smart house in a smart street in the region most favoured by Court physicians and the big-wigs of the medical profession, a class for whom I knew that my eccentric chief felt a very moderate respect. The house was brightly painted, and the windows were garnished with boxes of scarlet geraniums and blue lobelias. The brass plate on the door was burnished to shine like glass, and the steps were a dazzling white. Nothing could have been further removed from any suggestion of secret practices or unhallowed consultations.

The man who opened the door to us matched the exterior of the house as far as his own exterior was concerned. He was young and clean-shaven, his hair was beautifully brushed, and his neat clothes were as new and well-fitting as those of the man whom we had left lying in the alcove at the Domino Club. The face itself was that of a simple, harmless young man, incapable of suspecting either his master or his master’s patients. It was impossible to think that he had ever been aware of anything strange or doubtful in his environment, so innocent and fresh was his whole aspect. The very nervousness with which he received us was the nervousness of youth and inexperience finding itself in the presence of unexpected trouble.

Inspector Charles briefly announced his name and official character, and those of my chief, not deeming me worthy of individual mention. Tarleton promptly took the youthful butler in hand.