I went on to ask him a few questions about the case, premising that I did so in the most friendly spirit.  “Oh, I can only tell you what is publicly known,” he answered, beaming, with the usual professional pretence of the most sphinx-like reticence.  “But the plain facts, as universally admitted, were these.  I break no confidence.  Yorke-Bannerman had a rich uncle from whom he had expectations—­a certain Admiral Scott Prideaux.  This uncle had lately made a will in Yorke-Bannerman’s favour; but he was a cantankerous old chap—­naval, you know—­autocratic—­crusty—­given to changing his mind with each change of the wind, and easily offended by his relations—­the sort of cheerful old party who makes a new will once every month, disinheriting the nephew he last dined with.  Well, one day the Admiral was taken ill, at his own house, and Yorke-Bannerman attended him.  Our contention was—­I speak now as my old friend’s counsel—­that Scott Prideaux, getting as tired of life as we were all tired of him, and weary of this recurrent worry of will-making, determined at last to clear out for good from a world where he was so little appreciated, and, therefore, tried to poison himself.”

“With aconitine?” I suggested, eagerly.

“Unfortunately, yes; he made use of aconitine for that otherwise laudable purpose.  Now, as ill luck would have it”—­Mayfield’s wrinkles deepened—­“Yorke-Bannerman and Sebastian, then two rising doctors engaged in physiological researches together, had just been occupied in experimenting upon this very drug—­testing the use of aconitine.  Indeed, you will no doubt remember”—­he crossed his fat hands again comfortably—­“it was these precise researches on a then little-known poison that first brought Sebastian prominently before the public.  What was the consequence?” His smooth, persuasive voice flowed on as if I were a concentrated jury.  “The Admiral grew rapidly worse, and insisted upon calling in a second opinion.  No doubt he didn’t like the aconitine when it came to the pinch—­ for it does pinch, I can tell you—­and repented him of his evil.  Yorke-Bannerman suggested Sebastian as the second opinion; the uncle acquiesced; Sebastian was called in, and, of course, being fresh from his researches, immediately recognised the symptoms of aconitine poisoning.”

“What!  Sebastian found it out?” I cried, starting.

“Oh, yes!  Sebastian.  He watched the case from that point to the end; and the oddest part of it all was this—­that though he communicated with the police, and himself prepared every morsel of food that the poor old Admiral took from that moment forth, the symptoms continually increased in severity.  The police contention was that Yorke-Bannerman somehow managed to put the stuff into the milk beforehand; my own theory was—­as counsel for the accused”—­he blinked his fat eyes—­“that old Prideaux had concealed a large quantity of aconitine in the bed, before his illness, and went on taking it from time to time—­just to spite his nephew.”