“Dr. Vaughn,” continued Craig, as if goading him to the point of breaking down his calm silence, “you are specialist enough to know these things as well, better than I do.  You must know that epilepsy is one of the most peculiar diseases.

“The victim may be in good physical condition, apparently.  In fact, some hardly know that they have it.  But it is something more than merely the fits.  Always there is something wrong mentally.  It is not the motor disturbance so much as the disturbance of consciousness.”

Kennedy was talking slowly, deliberately, so that none could drop a link in the reasoning.

“Perhaps one in ten epileptics has insane periods, more or less,” he went on, “and there is no more dangerous form of insanity.  Self-consciousness is lost, and in this state of automatism the worst of crimes have been committed without the subsequent knowledge of the patient.  In that state they are no more responsible than are the actors in one’s dreams.”

The hospital physician entered, accompanied by Craig’s messenger, breathless.  Craig almost seized the package from his hands and broke the seal.

“Ah—­this is what I wanted,” he exclaimed, with an air of relief, forgetting for the time the exposition of the case that he was engaged in.  “Here I have some anti-crotalus venine, of Drs. Flexner and Noguchi.  Fortunately, in the city it is within easy reach.”

Quickly, with the aid of the physician he injected it into Veda’s arm.

“Of all substances in nature,” he remarked, still at work over the unfortunate woman, “none is so little known as the venom of serpents.”

It was a startling idea which the sentence had raised in my mind.  All at once I recalled the first remark of Seward Blair, in which he had repeated the password that had admitted us into the Red Lodge—­“the Serpent’s Tooth.”  Could it have been that she had really been bitten at some of the orgies by the serpent which they worshiped hideously hissing in its cage?  I was sure that, at least until they were compelled, none would say anything about it.  Was that the interpretation of the almost hypnotized look on Blair’s face?

“We know next to nothing of the composition of the protein bodies in the venoms which have such terrific, quick physiological effects,” Kennedy was saying.  “They have been studied, it is true, but we cannot really say that they are understood—­or even that there are any adequate tests by which they can be recognized.  The fact is, that snake venoms are about the safest of poisons for the criminal.”

Kennedy had scarcely propounded this startling idea when a car was heard outside.  The Rapports had arrived, with the officer I had sent after them, protesting and threatening.

They quieted down a bit as they entered, and after a quick glance around saw who was present.

Professor Rapport gave one glance at the victim lying exhausted on the bed, then drew back, melodramatically, and cried, “The Serpent—­the mark of the serpent!”