“What strikes me, sir, that all the persons whose names appear in your list were old frequenters of the club. They had had many previous opportunities of drugging Weathered. Last night was the first occasion on which his step-daughter was present, and last night was the first time he was attacked.”

Tarleton accepted this argument more amicably.

“Now you have made a real point. It might be a good point if there were no other suspicious features in the case. But it is open to this objection that your argument cuts both ways. Sarah Neobard lived in her step-father’s house, and had every opportunity of administering drugs to him there. Why should she have chosen the Domino Club for such a purpose? And if her object was to obtain his keys, she might have managed that when he was asleep at home far more easily than anywhere else. That’s the one point we mustn’t lose sight of in this affair—that the motive was to gain access to Weathered’s safe. Revenge was a secondary consideration.”

I felt myself fairly cornered. Prudence compelled me to assent to my chief’s reasoning.

“I will ask you to make a copy of this final list and send it round to Captain Charles,” he went on to say. “The police may be able to find out something about these twelve persons which will narrow the inquiry down to one or two.”

I held out a hand that almost trembled for the paper, and hastened to fold it up and slip it into my pocket. The thought had instantly occurred to me that I might omit one name in the copy to be sent to the police without much risk. If the omission were discovered it would be put down to carelessness, and meanwhile time would have been gained.

Tarleton had risen to his feet.

“And now it is time to examine the body,” he said gravely.

I followed him out of the room and into the laboratory, where the corpse lay stretched on a marble slab, ready for the surgical knife. The sight distracted me for a time from my other anxiety. I was profoundly puzzled by the symptoms I have described already. The grayness I had remarked had grown deeper, and the whole surface of the skin was corrugated by tiny wrinkles, so that it presented the appearance of a mummy dried by the embalmer. It was impossible to attribute these signs to the action of opium in any quantity of which I had experimental knowledge. My heart sank as I remembered the ominous pronouncement of my chief. If he were right, and another drug, more deadly than opium, had been administered by an unknown hand to the masked Inquisitor during last night’s revel, the situation would be terrible indeed. The murder, the deeply-planned murder, as Sir Frank had termed it in advance, would be attributed to the same hand that had abstracted the keys and carried off the case-book from the safe.

The proceedings in which I had now to play the part of assistant were of too gruesome a nature to be described in anything but a medical report. It is enough to say that the general result was negative as far as my medical knowledge went. There was no sign of any organic injury. There was nothing in the condition of the heart to explain the fatal event. The internal symptoms corresponded closely with the external ones. Everything pointed to death having been brought about by the action of a poison similar in some of its effects to opium, yet having a peculiar influence on the interior membranes as well as on the outer cuticle. But what that poison was I was at a loss to tell.