There was not much that I could find.  Of Mrs. Maitland there was practically nothing that I already did not know from having seen her name in the papers.  She was a leader in a certain set which was devoting its activities to various social and moral propaganda.  Masterson’s early escapades were notorious even in the younger smart set in which he had moved, but his years abroad had mellowed the recollection of them.  He had not distinguished himself in any way since his return to set gossip afloat, nor had any tales of his doings abroad filtered through to New York clubland.  Dr. Ross, I found to my surprise, was rather better known than I had supposed, both as a specialist and as a man about town.  He seemed to have risen rapidly in his profession as physician to the ills of society’s nerves.

I was amazed after dinner to find Kennedy doing nothing at all.

“What’s the matter?” I asked.  “Have you struck a snag?”

“No,” he replied slowly, “I was only waiting.  I told them to be here between half-past eight and nine.”

“Who?” I queried.

“Dr. Leslie,” he answered.  “He has the authority to compel the attendance of Mrs. Maitland, Dr. Ross, and Masterson.”

The quickness with which he had worked out a case which was, to me, one of the most inexplicable he had had for a long time, left me standing speechless.

One by one they dropped in during the next half-hour, and, as usual, it fell to me to receive them and smooth over the rough edges which always obtruded at these little enforced parties in the laboratory.

Dr. Leslie and Dr. Ross were the first to arrive.  They had not come together, but had met at the door.  I fancied I saw a touch of professional jealousy in their manner, at least on the part of Dr. Ross.  Masterson came, as usual ignoring the seriousness of the matter and accusing us all of conspiring to keep him from the first night of a light opera which was opening.  Mrs. Maitland followed, the unaccustomed pallor of her face heightened by the plain black dress.  I felt most uncomfortable, as indeed I think the rest did.  She merely inclined her head to Masterson, seemed almost to avoid the eye of Dr. Ross, glared at Dr. Leslie, and absolutely ignored me.

Craig had been standing aloof at his laboratory table, beyond a nod of recognition paying little attention to anything.  He seemed to be in no hurry to begin.

“Great as science is,” he commenced, at length, “it is yet far removed from perfection.  There are, for instance, substances so mysterious, subtle, and dangerous as to set the most delicate tests and powerful lenses at naught, while they carry death most horrible in their train.”

He could scarcely have chosen his opening words with more effect.