At nine the next morning, I tested one drop of the culture under the microscope.  Clear and limpid to the naked eye, it was alive with small objects of a most suspicious nature, when properly magnified.  I knew those hungry forms.  Still, I would not decide offhand on my own authority in a matter of such moment.  Sebastian’s character was at stake—­the character of the man who led the profession.  I called in Callaghan, who happened to be in the ward, and asked him to put his eye to the instrument for a moment.  He was a splendid fellow for the use of high powers, and I had magnified the culture 300 diameters.  “What do you call those?” I asked, breathless.

He scanned them carefully with his experienced eye.  “Is it the microbes ye mean?” he answered.  “An’ what ’ud they be, then, if it wasn’t the bacillus of pyaemia?”

“Blood-poisoning!” I ejaculated, horror-struck.

“Aye; blood-poisoning:  that’s the English of it.”

I assumed an air of indifference.  “I made them that myself,” I rejoined, as if they were mere ordinary experimental germs; “but I wanted confirmation of my own opinion.  You’re sure of the bacillus?”

“An’ haven’t I been keeping swarms of those very same bacteria under close observation for Sebastian for seven weeks past?  Why, I know them as well as I know me own mother.”

“Thank you,” I said.  “That will do.”  And I carried off the microscope, bacilli and all, into Hilda Wade’s sitting-room.  “Look yourself!” I cried to her.

She stared at them through the instrument with an unmoved face.  “I thought so,” she answered shortly.  “The bacillus of pyaemia.  A most virulent type.  Exactly what I expected.”

“You anticipated that result?”

“Absolutely.  You see, blood-poisoning matures quickly, and kills almost to a certainty.  Delirium supervenes so soon that the patient has no chance of explaining suspicions.  Besides, it would all seem so very natural!  Everybody would say:  ’She got some slight wound, which microbes from some case she was attending contaminated.’  You may be sure Sebastian thought out all that.  He plans with consummate skill.  He had designed everything.”

I gazed at her, uncertain.  “And what will you do?” I asked.  “Expose him?”

She opened both her palms with a blank gesture of helplessness.  “It is useless!” she answered.  “Nobody would believe me.  Consider the situation.  You know the needle I gave you was the one Sebastian meant to use—­the one he dropped and I caught—­because you are a friend of mine, and because you have learned to trust me.  But who else would credit it?  I have only my word against his—­an unknown nurse’s against the great Professor’s.  Everybody would say I was malicious or hysterical.  Hysteria is always an easy stone to fling at an injured woman who asks for justice.  They would declare I had trumped up the case to forestall my dismissal.  They would set it down to spite.  We can do nothing against him.  Remember, on his part, the utter absence of overt motive.”